staff are we talking and what is the nature of the action so we've got to go all we've got upwards of uh 500 members who will be involved in this action uh nationally there's 12 000 workers who are involved in the local authority sector for for so we're the largest union in the local government sector now i should say that this right isn't uh new it's been going on for for a long time we've been trying to resolve it but essentially 10 000 council jobs were lost following the financial crisis and services were only maintained because staff have taken on additional duties above their pay grades across the the public sector and local authorities suffered the greatest reduction in staff numbers during the austere the year years and it resulted in what we've described Greg as significant grade drift so people working above their grade like we're after one thing one thing only it's fairly straightforward ask uh we want the management to introduce a job evaluation process which is essentially an analytical tool used in an organization to see if the post holder is being paid correctly for the work that they're doing or expected to do so can i can it does it so from a lay person or someone outside it sounds to me then what happened there was a lot of redundancies the remaining staff put the shoulder to the wheel uh took on extra duties uh no one questioned at the time because it was a national emergency that some of those duties would ordinarily uh go to someone on a higher pay grade but it became normalized and now here we are uh 15 odd years later and it's all been blurred now and people that are doing work uh that should they should be compensated more for yeah well i mean i think that that's it in a nutshell um i think uh what the job evaluation tool does and it's a common place across the hse and in the higher education sector lots of places in the private sector use it every local authority in the six counties and in england scotland and will uses it so there's no guarantee it's evaluation exercise to ensure that people are graded properly uh there's no commitments or guarantees for people who go into that process the human rights and the quality commission have confirmed that the job evaluation tool is good in terms of ensuring equal pay for work of equal value uh and we're now dealing with a local government management sector which is simply just tone deaf to the the reality that workers are no longer willing to act at a higher level and be paid at a lower level as it were and 85 percent of our members voted yes in a ballot to give us a mandate for action up to include the strike action uh so we kicked off the industrial action this morning Greg uh and that means that all of our members will will be refusing to engage in non-statutory political representations so verbal written and email from politicians and last wednesday i wrote to every councillor senator and tb in the country confirming the action would take place and apologizing in advance for the impact that this may have on the critical work of an elected representative so can we can you give us a can you give us an example of of a typical content from a politician that will now not be cooperated so politicians would particularly councillor would make routine contact throughout the working day of local authority staff ask inquiring about things that might be happening in roads or water or developmental works so that won't be responded to mandatory or statutory engagements will still be responsible responded to so workers will still prepare agendas for meetings and municipal district meetings and and help with the administration of the democratic structure as it were but that informal day-to-day contact is not uh won't be out here too but the councillors and the politicians will go back and say look i can do nothing i can do nothing for you the the staff won't work for me and blame you guys for that i mean is it not really the the the public that's going to feel the heat on this and you'll get the usually be the bad guys so actually the opposite has happened surprisingly uh or maybe not surprisingly like in bug and say council of the weekend uh the political leadership of all the main political parties and the the independent group and signed a motion to go to council supporting the uh the the force action so up and down the country we've had really positive feedback from councillors, TDs and senators uh and and in this county and doing all we've had a lot of feed a positive feedback and support because i think people realise that hard pressed local government staff have had enough and they're you know really people are working above grade and i think it's seen by people in the political system that it's no longer sustainable so once you're right we're not in dispute with politicians this is workers exercising their democratic right and not to do part of their work as part of the the ongoing dispute and i assume the staff are saying look we're not we're not looking for pay rises we're looking for the pay we're working what you do that would be the the argument and as you say if this evaluation tool is used there's no guarantee that that someone might get a pay rise i mean obviously they'll suspect they'd have a fair chance of it but this is about being paid uh as you should be for the work you're doing rather than seeking a pay rise so so it's a precursor step actually it's just the ability to have your job independently uh assessed or allow to see if you're doing work at a higher level and i should say this there is no guarantee that that would be the case but there's a recruitment crisis in the local government sector i remember speaking to you years ago during the financial crisis and dunny ball lost a disproportionate number of those those jobs so local government was once the employer of choice that's now no longer the case people are voting with their feet and there's a recruitment and retention crisis in the local government sector as people go and workouts were including the private sector so we think that this is a good to to keep people to maintain people to ensure that we have people across the six public services centers in dunny ball for instance to deliver key services to to to the public and uh like we would prefer not to be in this position the ask is modest just give us the process on which to deal with with the issues to ensure that people are validated uh properly and the local government sector management grega should say this they've said two things in the same breath which is contradictory they've said in the one hand everybody's created properly and there's nothing to see and in the same breath they say if there is job evaluation it's going to cost a fortune and everybody will be regretted I would I would say in response to that it can't be both it has to be one or the other right so the dispute is well they don't trust they don't trust the mechanism as far as they're concerned now is the status quo moving forward why upset the apple card uh and they fear obviously that this this evaluation would rejig things to the point where people would have to be paid more money Rich you've got a broad mandate from from your members uh force members how does this escalate because you know of course this is the type of action whilst it's important and it's significant it falls off the the news cycle really quite quickly uh so you know what what is the next action when are we likely to see that I don't think it's going to go away anytime soon I think that the part the political response has been really overwhelming and politicians have been writing the minister Daryl Bryant seeking from the intervene uh and and county councillors have been placing down emergency motions at council meetings but there will be an escalation over the common weeks as a result of this and and definitely could result in workers pulling out and putting boots on the ground with full blown strike action so a small window of opportunity Greg exists for the the local government management to engage in a sensible solution focused discussion under the auspices of the workplace relations commission my phone is on and I'm waiting to hear if anybody wants to make contact within the political system or within the local government management agency to go back to negotiations and back to talks but the right isn't going to go away by simply pretending it doesn't exist now um the local government management agency who you reference they're saying that you know yes both both parties went into the WRC and the matter could have been referred to the labour court but instead you decided to commence this industrial action and say that this is contrary to the provision of the public sector pay agreement building momentum what do you say to that what says you uh well that's you know I've heard this line throughout um we the dispute was supposed to take off in late June as a result of discussions between myself and the leadership of the LGMA we referred the row to the WRC and the terminology we used was that both parties would engage constructively and meaningfully in order to resolve the row we had two goals of it at the WRC it was neither constructive nor meaningful uh and therefore talks broke down um this isn't legitimate because workers are kept fed up and they're now open with our feet but but but it is avoidable and it is solvable right so we remain available for meaningful discussions under the auspices of the WRC Greg you've been covering industrial disputes most of your career certainly for all the time you've been working in Highland it normally ends in some negotiation somewhere where people can live with it will require given take on both sides but we can't negotiate on our own and the LGMA need to put their shoulder to the wheel and need to be serious and go back to the negotiating table otherwise this is going to continue and it's going to escalate all right well between the jigs and the reels I don't think Dara O'Brien's going to be booking uh a month in downings next summer but anyway thanks very much for your time take care all right that is Richie Carothers assistant general secretary of the force union and the reference there of course is that it's minister Dara O'Brien who is the go-to guy there and he's hearing plenty from Donegal listening open to discussion but certainly hearing plenty it is the 9 till noon show at half past 11 how are you all back with him all back with more for you very shortly watch the show live now on youtube facebook and at highlandradio.com the 9 till noon show with letter kenny credit union now offering mortgages from 40 000 to 600 000 euro with no hidden fees or transaction charges letter kenny credit union 9102127 don't miss the big baby event at Lidl mix and match multi buys across our award-winning loopy loop premium nappy's range from two packs for two euro get dreamy prices on 100 cotton baby's sleep 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built for a better world terms and conditions apply there's bingo every monday night at halfway house bingo burn for doors open at 7 30 with eyes down at 8 30 2,500 euro musko the snowball is now 1,500 euro on 45 numbers or less if you're not in you can't win that's halfway house bingo tonight at 8 30 a public interest message from tony gall county council overgrown hedges shrubs and trees along public roads can become a danger to people using or working on a public road dunny gall county council is reminding landowners and occupiers of their obligations to trim hedges and trees beside the public road this should be done before the bird nesting season commences in early march dunny gall county council thanks to many members of the public who have already carried this work out dunny gall county council supporting communities and the environment okay now as part of it's monday focus time by the way as part of palliative care week 2023 the all-arland institute of hospice and palliative care is calling on people in the northwest to become better informed about its benefit the campaign reaches its milestone tenth year this autumn will take place on the tenth to the sixteenth of september so we're in that week now this week and this item aims to educate people across the region about the positive impact that it can have on life quality and to encourage them to learn more about the services available should they need them in the future Karen Charnley is director of all-arland institute of hospital sorry hospice and palliative care and is with us now good morning to you Karen good morning Greg it's lovely to have you on the program are we getting better talking about this stuff now i get a sense maybe it's because i'm getting older and i'm really talking about how i feel but do you know it is it kind of wee bit like wheel writing and stuff maybe you know when we are in good health for those around us are we tend to either avoid or just choose not to talk about you know hospice and palliative care well we commissioned a survey to inform palliative care about people's perceptions and we found that 40 percent of adults prefer not to think or talk about palliative care and 50 percent of adults think that palliative care if someone's receiving palliative care it means that they're in the last days or weeks of their lives so for us this shows that misconceptions about palliative care persist which mean that some people who could benefit are less willing to seek it and potentially missing out on the quality of life benefits that palliative care can provide some people can live long and the aim is uh fall or fall as possible lives whilst receiving palliative care yeah but it isn't just about that end end of life i suppose in some instances it is last days and weeks but what we that palliative care can be received from diagnosis and prognosis onwards within someone's journey and um the the thing is is we don't want to talk about it but lots of us who've had someone who's passed on either under the care of a hospice or in palliative care and all both it is often a positive a positive element of a very difficult experience and that's where it gets difficult to talk about but that's why people fundraise so much for these types of services because they understand how they can improve people's quality of life with a terminal diagnosis yeah i suppose people and i suppose it's understandable maybe people don't want to think and talk about it don't want but what we'd encourage for encourage people to learn more about the benefits of palliative care also to have those conversations with family members and friends you know loved ones and about how they'd want to be cared for where they'd want to be cared for because i suppose the research evidence suggests that you know that those conversations can be really supportive when the need arises in the future that people can feel that they're honouring meeting someone's wishes so hold me by the hand and lead us through it then you know sort of what we're talking about here when to have the conversation how to have the conversation even maybe how to plans or preparations in in finding what resources we might be talking about locally because i think that's where the problem is then it becomes we perceive it to be complicated so talk us through Karen what we're talking about here well i suppose thinking of different information sources i'd encourage people to look on the palliativehope.com we have a series of websites with a lot of information around this area and also the one of our member organisations the Irish Hospice Foundation have developed the think ahead pack which really is a is a document but it gives people the prompts they'd need ask them the questions to allow people to start planning ahead for the care that they'd like but what we've very much said i know even with my parents at home having those conversations about well where would you like to be cared for do you would you like to be cared for at home or would you prefer if the need arises and symptoms arise would you like to be cared in the hospital or a hospice having those important discussions and thinking ahead about the type of care people would want it it's kind of important to have those those discussions yeah and how do you have them is there any advice on that because you know i know in my parents situation god rest the two of them that if and i had a fantastic relationship with both don't get me wrong but if i went in and i says to my dad who was 16 in his head to the day he died can we talk about he i would have been chased do you know what i mean now obviously you can't compel people to have these discussions but how is the best way to approach that i wonder i may be taking the prompts maybe at the you know if someone's i know my own father again using him as an example he had a serious problem with his eyes and that did open the opportunity to have some of these discussions to say well what you know how would what are the plans for the future where have you set out your plans so sometimes there might be good opportunities suppose we can't force anyone to have these discussions but i think it's raising that it would be useful to have them with with family members and also to the other side of it and we're all different but we kind of fall into similar categories i think i would say there are people maybe who are getting a little bit older that there's a bit of stress and anxiety as to what might happen to them do you know what i mean and they don't want to bring it up either so actually probably for for some if not many would be a welcome conversation we may never need to go down this route or but if we do do you know what i mean so there's a piece of mind and a person feels they have control over their over their future well and i think it's for all concerned that you you know as a family member that you're being clear about what type of care they want because i suppose we all have different views like some people may want to be careful completely at home other people would be happy to you know be cared for in different settings i would also flag that say and you mentioned around local hospice services so don't go all hospice this week they've got a wide range of events taking place throughout the week so in letterkenny university hospital hospital they're having information stores from 12 to 4 in the staff dining room in donagall hospice they're having an open day on wednesday from 2 to 4 and they're encouraging people to come and visit the hospice or they've also got pop-up stands in letterkenny shopping center and macklehenny's in ballet boffy on friday from 11 to 3 as well so they're really supporting palliative care week and we're very appreciative of that and pardon my ignorance caron when we talk about the planning and the conversation it's not like booking things or or securing things is it it's knowing people's wishes and what what they might want given what circumstances may arise isn't it so it's really planning to it's really planning isn't it to fulfill their wishes rather than actually to say right you're going here and you're going there and you're going there you know what i mean no you wouldn't be booking someone in somewhere but it's to have start having those conversations that's why i'm like the thinker head form it's really you know only people google but also if people visit the palliative hub dot com there's lots of resources but it's those prompts about thinking of the future but i suppose like during palliative care week we're keen to kind of highlight the benefits of palliative care and how it supports people's physical social emotional and spiritual needs and puts the person at the centre of the care and that if people were under the care or you know when the need arises under the care of palliative care that they'll be those services are there to support them with planning ahead as well so um so sort of jumping backwards to the maybe something might talk to at the start so like what is do people resist engaging with palliative care what do they do as an alternative do you know what to mean well i suppose sometimes and we we'd hear that people yes but are resistant to accessing those services or might not seek them out because they often think oh it's the last days or weeks of life when in fact people can be under in receipt of palliative care for a wide long period of time and it might be that the access services and then a discharge from services as they no longer require them so i suppose again thinking of a family friend to have that they he was in receipt of palliative care service was in the inpatient unit the unit was able to support them with symptom management he was discharged back to home he's currently under community palliative care services and he's still he has advanced cancer still receiving treatment as well as part of that so often people sometimes think palliative care last days last weeks and there's no other treatment being provided when in fact it can be that you know palliative care can come in and out as needed and is there as a supporting service along with people's other medical specialties be it if they've advanced cancer heart failure renal wrong conditions neurological conditions and the like and in providing these services and supports and people do it to the absolute best of the ability a lot of the time it is sort of interacting with other areas of of health service and presumably you know the same challenges exist for palliative care providers in engaging with the other areas of health that do for the you know the population as a whole but I suppose that being said though there is a level of knowledge and experience there that would mitigate as much as is possible those frustrations yeah I suppose is palliative care teams are well used to engage in with people's other medical teams as well so that is really the focus of those services as well so yeah what other interesting findings or findings of an old came from that survey in your view Karen well we did find with the survey results that people do have a good sense of palliative care so there was positives as well that for example nearly 1810 adults agree that palliative care also supports families, friends and caregivers seven in ten think that palliative care should be considered as early as possible when diagnosed with a life-limiting conditions so there is a number some of the stats that are showing that people do have an understanding but there still are some misconceptions and that's why we're this is our 10th year of running palliative care week so but there's still more work to be done in terms of supporting people to learn more about palliative care and its benefits yeah for sure where can people get more information well I'd encourage them to look on our website which is the palliativehug.com and on there there's lots of campaign resources and leaflets we also have videos of people's palliative care experiences we there's also a wide number of events taking place and I've already mentioned some that are taking place within your own county but there's details of a lot of events both face to face but also online events that people can register and attend and we'd encourage them to share their experiences on social media using the hashtag palcareweek10 but the palliativehug.com has got a lot of information on it so I would encourage that as a first stop to then find in other services that and supports that are out there all right Karen listen it's been lovely having you on the show thank you very much indeed Karen Charney there who is a director of all island Institute of Hospice and palliative care we are in the midst of palliative care week 2023 kicked off yesterday as you heard some great events there for people to attend if you so wish now I want to mention to you it's a year out but the spaces aren't necessarily open-ended either David James is leading Highland Radio's Hooli to Saloo in 2024 it runs from the 14th to the 21st of September 2024 and it is your summer sorted late summer sorted for this type of event there's music for Margo John McNichol Robert Marcell Hugo Duncan Claudia Buckley Matt Levy Sean Cuddy Olivia Douglas Gavin Gribbin Jim Devine Schnee Black The Ryan Turner Band and on and on it goes there's two more here but I mentioned Shawnee Crampsey and Trevor Lockery so for 817 euro per person you get access to all of those stars with night time shows poolside shows you get seven nights B&B in the four star soul coaster Dorada Hotel seven nights dinner B&B so your dinner and your breakfast is sorted your hotel accommodation is sorted and all your entertainment is sorted for 817 euro per person so you can spread that out in your mind over the year it might be well within your means now that includes the price all access to shows airport transfers for dinner each evening with wine 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he met a lot of tourists from a number of different countries but there were no restrooms facilities in the area for people to use the bathrooms or even wash their hands sometimes you wonder we might get gates before we get parking there and on it goes more of your comments here to come on the way but we're going to take a short break stay where you are back with more after these at the Central Statistics Office we're trusted to gather all sorts of information so we count lakes stakes and haulage intakes we count wages ages and all of life stages we count loans phones still living at home we count euros and cents and housing and rents we count Mars electric cars and the price of a jar because this data informs important decisions on everything from economic activity to housing policy to what to call a new baby and we can't do it without you CSO count on us we count on you Alzheimer's Memory Walk takes place on Sunday, September 24th nationwide will you join us and walk for the 64,000 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Register now for your pack and find a walk near you at memorywalk.ie or call 01-207-3800 let's walk together Alzheimer's Memory Walk supported by Payzone if you know the beauty and skincare product that suits you best you'll find them at McGee's Chemistry from moisturizers, cleansers and toners to day creams and night creams McGee's have the top brands you know and love like Longcombe, Clarence and LaRouche-Posay also Elizabeth Arton Fishy, Nukes and many more all at McGee's Chemist Main Street Let it Kenny and online at McGee's.ie for the best costs less Hi folks, Tommy Devill here inviting you to join me self and Jimmy Stafford this Monday night for another edition of the Monday Night Sessions on the show this week we give a big welcome to Straban singer-songwriter Darcy Wilders and we also give a big massive welcome to the winners of this year's Let it Kenny busking festival the Let it Kenny ukulele orchestra so that's the Monday Night Sessions this Monday night between 8 p.m. and 10 p.m. right here on Highland Radio Right, we're joined on the program now by Councillor Donal Mandi Kelly thanks for taking the time to speak to us Donal good morning to you Hello problem Greg good morning to you and good morning to all your luster great Right okay so you finally got to sit down with Ishka Ayer and formerly Irish Water a long time coming a useful meeting do you feel Yeah Greg the lesson I suppose anytime you get out scared and the senior executives or officials in front of you it's it's positive for more going lesson as you stated that was definitely a long time coming something that pushed hard for myself as did other counselors as well for a long number of years but lesson we finally got to meet them face to face and what's part of rig every counselor got their opportunity to I suppose raise raise issues on their own and behalf of their constituents and you know that that was very very important and I feel it was part of person there's a lot of there's a lot of issues to be aimed at what's that scaring as well and that's what we keep doing that pushing forward but I suppose that's easy to do when you've got dates and timelines which we have for some of the issues and of course you're going to be focusing on the letter Kennean surrounding areas Bombay and Tolley Gay residents in those areas are subjected to regular outages 11 in 14 days what was the update for Mishka Erin in relation to that situation yeah Greg is a fully aware of the trunk and I've been pushing hard for the residents so Bombay and New Miles pull again common areas and as you said there are 11 outages and 14 days and that has actually increased since the meeting as recent as yesterday and the day before there's no water either I was very strong unless most officials of Mishka Erin and I wanted this addressed as a matter of urgency I did ask them because they had stated to me before that they were committed to addressing this issue in the first quarter of 2024 and thankfully this is still scheduled to commence in the first quarter of 2024 and is it actually work or explorer to work do they recognize the problem for that area and have a plan in place for early 2024 to actually fix it yeah that's what they're telling me Greg listening that they carried out had analysis assessment on what that is showing up at the moment seems to be issues with boss and vows but they have as I stated the happy put on the infrastructure on the ground there for them residents they haven't come at it looking into this now and to address it on the first quarter of 2024 and another another thing I also raised them Greg regarding and that area was well well you know I raised very strongly that the look at the lot there there it's a lot that's up between them the mountains in church needy and and and church there between kind of what the one miles are you know and this listen as I said in the meeting it might be viable but it was snaps and that a vast Irish water to look under because I think it could be a solution the resolving issues along that area there bombing new malls and all because that would feed right down on to it and listen that they took it on board and they are going to look on to it and you know I think it's something that could work out positive but Greg the most important thing is as this the works that are scheduled for 2024 Irish water did clap to me at the meeting that they are going to be pushing forward on so you know that's a good news story for the rest and stuff of these areas and I will be I will be keeping pressure on to ensure that this work goes as soon as possible you also got a commitment that work is going to start in November in and around the Ross Bracken and Mannequin areas but there are rather hot spots were there any is there any particular areas whereby they didn't have anything positive to say well listen your rate of getting Greg that works and that's very welcome the Ross Bracken and Ray Moche they already start now in November of this year the one they're going to be really in a 2.6 or 2.7 kilometers of new pipes there new infrastructure for all them rest and so that should resolve the problem there listen there's all our contractors have issues in their own areas that that they weren't happy with and weren't been addressed and I suppose even as Michelle there you know I raised the issue there and a house I said in particular there that I've got a number of calls and that the Kinney is own hull and there seems to be a problem there with the storm why there seems to be connected to the sewers and listen I have been pushing and looking into this and the Duneagall County Council they have said that it's under the authority of Irish weather and Irish weather don't seem to want to take responsibility for it so I have asked for answers on this no I didn't get the answers on the day but they are very back to me and I will be following and open it because this is something that needs to be addressed but I've stopped there and metal threads and some own hull and we're seeing pictures as well where we're one's having rain Greg the sewers has actually come out of the storm lanes you know and it's absolutely shocking all right okay but listen there's a lot of work for the Irish weather they need to need to commence with and they need to get the finger out you know and we another thing were very strong ones were was the connection fees I mean that's absolutely ridiculous some of the connection fees the cost such people have been asked them and just give me maybe one example Greg if you don't mind no go ahead that's that's actually a house not fire from yourself well they've done a native 180 meters of mains piping to run and you know they were they were Irish Wather give them a value of 43,064 euro to take 100 meters of mains Wather up to the house you know that's just absolutely shocking and you know when I asked them to narrow this down that I'd worked out of the standard connection fee of 2,272 euro the cost of taking the 180 meters was working out of 27,381 euro but the problem is there is a not that they and cause another four and a half thousand it's terrible but the problem there is we don't have time they've farmed that out to private companies to do that though so that might be difficult to get some movement on yeah well that's just on Greg we're just gonna have to keep the finger on and keep pushing forward on because that's just that's only one example let's just right through the county and the conflict that matter where people have been given ridiculous costs for connection fees you know and a shocker now Donald thank you so much so thank you so much for your time this morning and we'll get an update for you as soon as you get anything back from them on the other concerns you raise with them for now though thank you Councillor Donald Mandy Kelly that's where we have to leave it on the program today thank you to the team behind the scenes Donna Marie Daherty and also Neve Shields we'll be back with you tomorrow morning at nine stay tuned John Bres...


That song may go on for a while. I don't know. I can't remember exactly how it goes. This song may win some award for like, well, I don't know. There's probably a, I wonder what this best song is out there that actually has the fewest lyrics, right? Is there any awesome song where they just say one word over and over again? Or like two words? What's that? Part of like a rock star. Oh, OK. I've never heard that. Anyway, you guys can go figure this out at home. Like the best, you know, the Pareto optimal song in terms of the fewest number of words and most awesomeness. You can define that in a font. All right, so today we're going to pick up where we left off last time talking about how file systems handle failures. So I'll present a technique called journaling. And journaling is actually kind of an interesting approach, something that is applicable in other scenarios. And it's actually something that's done in other scenarios by databases and other types of systems to recover from failure. So it's a general enough idea that it may be useful to you at some point in the future. And it's certainly been useful in the context of other non-file system systems. And then we'll see how far we go. I don't think we're going to get through all this today. This is a lot of material. But at that point, we're going to talk about two classic file system designs. The first one, which I think we will get to today, is the Berkeley FAST file system. This is a oldie, but still sort of goodie. FFS introduced a lot of ideas into the file system space that you guys still are familiar with, because they're still out there. So certain design decisions and certain features of modern file systems are sort of inherited from FFS. And then LFS, the long-structure file systems are fun, and it's a fun sort of really controversial take on the idea of file system design. And a cool chance to see how a really radical redesign of file systems was motivated by a change in performance characteristics of the underlying system. To some degree, this is what happens in systems all the time. It's the relationships between different parts of the system change, new ideas come into the space, we revive old ideas, certain things work that didn't work before, et cetera. So this is a case where the ratio between a couple of the components on the system in terms of performance changed, and people argue that this justified a different approach to how you do file system design. OK, please work on assignment three. The second part is kind of out. I think Scott's going to push some upstream changes later tonight, and the targets for you guys to use for the second part of assignment three. We're also going to be a little bit more specific about some of the design requirements for your solution. Essentially, you cannot turn in DumbBM. We will do as much as we can to make sure that your solution is not DumbBM with a page alligator that works, or a souped-up version of DumbBM with like five hard-coded regions or something like that. Your solution also needs to support paging as opposed to segments, which is what DumbBM uses. And again, we will do our best to test those things. So if you are starting with DumbBM and thinking you're going to just rev up DumbBM a little bit and turn it in, please don't do that, we will try to make sure that doesn't work. Thank you, Ali. Someone keeps stealing my water bottles in the department. It's very odd. Anyway, either that or I'm losing them. I don't know. At first, I thought I was losing them. Now I think that someone is walking off them. Write my name on my next one with a big marker. Okay, so due to miscommunication between Ali and myself, the midterms are not ready. We will have them for you later in the week. We need to take them over and get them scammed. If you're really desperate for your grade, come by while I'm in the office and I can tell you your score on assignment three. But we'll have those back. Overall, the class scores, unlike last year's disastrous midterm, which required me to spend like a whole half lecture building up people's confidence again, this midterm was not the bet. The average, the median score was about a 33 out of 50. So that's kind of right where I like it. And we'll turn those back. Last year it was like a 13 or something out of 50. So that required some conversation. So I think this year's midterm was a little more appropriate. There was one perfect score this year, which is I think the first time that's happened. So that's cool. All right, any questions about the file system stuff that we've talked about already? I'm just gonna kind of plow onward. Okay, so remember the problem here is that I've got a bunch of things I need to change on the disk. Because of caching and other reasons, those changes sometimes make their way down to the disk at different points. And if the disk fails at some point where it's the on-disk data structures are not consistent, I can have various types of corruption. Some of the corruption can be really bad. I can cause entire files to disappear. It can cause their contents to disappear. I can leak space on the disk. I can mark things that are allocated that aren't allocated, et cetera, et cetera. But all of these problems are things that file systems try to avoid. So let's talk about another way of doing this. What we did last time was we said, you know what, we're just going to try to make sure that we understand the cache behavior. And when we're writing out parts of the file system that need to be written out consistently, we'll make sure they write through the cache and go to disk immediately. However, here's another way of doing things. So the observation in journaling comes down to the following. What's, if I think about the disk itself, what operation on the disk is not, you know, what's not atomic is writing a bunch of disk blocks. So regardless of whether I'm talking about flash or a spinning drive, if I need to make changes to a number of different parts of the disk, I have to make those changes sequentially and there are gaps of time in between them, particularly on a spinning disk where I've got to move the heads around and stuff like that. So any operation that requires writing multiple disk blocks is not something that I can do atomically. And so if I'm interrupted in the middle of it, I can have corruption on the disk. So I can have an inconsistency. However, if writing multiple disk blocks is an atomic, what is atomic or at least more atomic? What operation, so multiple disk blocks, you can mention on a spinning disk, I've got to move the head here, write one block, move the head over here, write another block, move the head over here, write another block. What would be potentially atomic in this situation? Yeah. Just writing one block? Yeah, so I write one block. So that block, to some degree, that block will either be completed or not. Now technically there's like this tiny little gap of time there where I'm actually doing the right. And so it's possible if my failure happens at exactly the right moment, I still might have like half the block written. But still to some degree that block didn't finish writing. And the time gaps are much smaller because I'm not seeking around the drive. So what I can do is I can use that as a starting point to build up an approach that allows me to atomically store information about what was supposed to happen to the disk, the operations I was supposed to be doing, and then using that atomic log to check and reconstruct other parts of the disk. So let me also just quickly contrast this with the other approach. So does anyone ever run like FSCK on their drive? So there are tools out there that will check the integrity of a file system. So you can take this tool and one of the things you can imagine it would do is it goes through and it builds up a model of the tree that the file system is supporting and make sure that there are no disconnected inodes and things like that.  What's the problem with using a tool like this? Somebody make a guess about this tool's performance. What's that? Well, okay, so let's say conservatively this tool in order to check the consistency of all the on-disk data structures has to touch how many disk blocks? All of them. Every block that has something in it, whether it's an inode or a data block potentially, I have to touch those and that's terrible. That just takes forever. So these tools are really slow. What's a problem with this? Say no problem, who cares? I'm not gonna have to use this very often. But why would it be a problem if that, because some of these old, I mean they did a great job, some of these old disk consistency tools, you can run it on the file system. And in like 12 hours, it would complete and you'd have some information and it might be able to fix some things automatically or whatever, but why is that such a problem? Yeah, it doesn't really matter how it's loading the system. Yeah, Zach. The disk is offline usually during these times. Now eventually you had fancier versions of these that could run in the background, but just imagine that I have to take this system offline for half day to fix this. So it's hard to get to four nines or five nines or six nines of availability on something like, now for your own personal machine, who cares? I mean, this explains the enduring popularity of the Windows defragmentation tool. It might take seven hours to run, but it's really fun to watch. It's like a video game. Who cares? Unless your system is serving as some sort of hidden torrent node or something like that, and no one is really affected by this.  Not only did the server go down, and do I have to bring it up again, but oh yeah, you have to sit there for half a day while I check the integrity of the file system. So not okay. So this is not really good or acceptable. So how can we limit the amount of things we have to check? There's the technique called journaling, which is really common in modern file systems. JXD4 supports it. Most modern file systems support journaling as a way to improve recovery performance. So what do we do? We use the journal to track the changes that we are going to perform to the disk, and the journal keeps track of when those changes actually make it to disk and are fully committed. You can think of it this way. So I check those changes in the journal, and remember, the journal is more atomic than making the changes themselves. So you can imagine that I can read, I can write to the journal, I can set up the journal operation so that a record in the journal fits inside a disk block, and then it's atomic to actually update the journal and say that I did something or I was going to do something. After a failure, I use the journal to figure out what is still inconsistent about the disk and bring it up to date. So rather than having to check the entire disk, which is what these old F-sync approaches would have to do, the journal-nate approach allows me to focus on the parts of the disk that might have problems and make sure that they're in a consistent state. So let's walk through an example of how this might work. So here's an example of a journal entry, and this is obviously not what would be on the disk, although it would be funny if you implemented it this way. Here's what I was in the process of doing. I was going to create a file, and we know the multiple different operations that this requires. I have to allocate an inode, I have to find some data blocks, I need to, and then I'm going to put the inode in a particular directory. So this was something that I was doing. So before I actually go about making the changes to the disk that this would require, I write this down in the journal. Here's something I was in the process of doing. Then once all those operations are completed, so you can imagine this, without the idea of checkpoint or to be able to remove journal entries, the journal would just grow forever. What happens is once I know that all of those operations have been completed, I can mark that entry as completed, and when I have a whole batch of entries up until a particular point that are completed, I call that a checkpoint. So when I flush a certain number of changes to disk, the system can figure out all the journal entries that have now where the on-disk contents are now consistent with what I was trying to accomplish, and those I can get rid of. Those are done. So this is called a checkpoint. Checkpoint means the point at which there's a point where everything before that point in the journal is on disk, and not necessarily everything after it is on disk. Does that make sense? Some of the things after it may have made their way to disk, but not all of them. But the point of a checkpoint is everything before the checkpoint has been committed, all the on-disk operations required to reflect that state are done. So here's one way of doing this. Once I've, once, now one of the things this allows is this allows these things to happen more slowly. I don't have to flush all these things to the disk immediately and create a lot of IO. What might happen is over time, I might do something like associate the data blocks, because the file might get used, but some of the other changes might linger in the cache for a little while before they actually get crossed off my list. But once I know that all of these operations are done, and all this data has made its way to the disk through the cache, I can mark this journal entry as complete, and I can put a checkpoint below it, or below all the other entries that are finished. Now what do I do when I recover? So let's say that the system crashes, doesn't shut down cleanly. How do I use the journal to, how do I use the journal to guide the recovery process? What's the algorithm here? What's a good starting point? Yeah. Yeah, so I back up to the last checkpoint, because remember the checkpoint guarantees everything preceding it in the journal is on disk. So I know that already. You know, I wrote that down before I crashed. So I back up to the last checkpoint, and then what do I do? Yeah, I use, this is called replaying the journal. I use the journal to check to make sure that the things that I was supposed to do are done. So I start at the last checkpoint, and I work forward through each entry, and what I do is I check the on disk data structures to make sure they're consistent. Because remember, the checkpoint doesn't mean that all of the operations below it aren't on disk, it just means that not all of them are. So some of those operations might be done. So I might take this, and I might say, okay, I see that I already allocated I node 5567, that's already marked as in use. Okay, that had been flushed to disk. You know, oops, I forgot to associate these data blocks with the file, I'm gonna do that now to make sure this is up to date. Gonna add I node 567 into the right directory so that it doesn't end up in lost and found, hanging out there. And once I get to the bottom of all my journal entries, I'm finished. And now the nice thing is the disk is up to date, it's in a consistent state, and I've touched as little of the disk as possible. Does this make sense? Any questions about this approach? Yeah. Is it possible for the journal to get kind of corrupted on this power? Yeah, so what happens if I have an incomplete journal entry? They're ignored, right? If I have an inconsistent entry at the end of the journal, like let's say, again, let's say I either had a journal entry that spanned a couple of blocks, and so I only wrote out a couple of them or whatever, those just get ignored. So journals are not a magic silver bullet to data loss after a crash. I'm not gonna say it's impossible because maybe somebody will make it possible soon, but it is very, very hard for a system, a file system, to guarantee that it will not lose data during a crash. But at least what the journal allows me to do is to get back to a consistent point where I know that the file system is in a consistent state. And that's really what I want to do. It's okay if maybe there was like one write or one append to a file that I didn't finish. Okay, so there might be a little data loss here, but at least if all the onto-status structures are consistent, I have a good starting point for moving forward. So in this case, if I got halfway through here, actually what I would probably do is undo this journal entry, make sure that these changes are not on disk because otherwise I would leak some of this information. Also, if the file system crashes, but what happens if the file system crashes before it actually writes the journal entry? What do I do in that case? I mean, nothing, right? That's data loss. There's no way to get around that. If I was about to do something and I was in the process of writing the journal, which I always do first, and I didn't even get that far, then sort of by definition that operation is gonna be lost. But again, that's okay. It is not the goal here to prevent all data loss after some sort of crash. That is impossible, right? Don't try to bend the spook. What is possible though is to make sure that I can rapidly bring the file system into a consistent state where I can start up again. So one other thing I wanna point out here, which is kind of interesting, one of the, you might have noticed in the, when I wrote this journal entry, let's go back here. This is, the journal entry here reflects changes to the metadata. The free, you know, iNode bitmaps, the free data bitmaps, things like this. It does not reflect, like if I was doing an append or a write, the journal here does not reflect the contents of that operation. So this allows me, in the sort of the model that I've showed you, this allows me to ensure that the file system metadata is up to date, but it does not guarantee that all, that file operations that might have been going on, like there might be some data that hadn't been written to the file yet. And that's not entirely, you know, that's an, I think that's an okay design trade-off. It is more important that the file system metadata and data structures stay up to date, because if those start to get wonky, you have a huge problem. If I lose one or two writes that were going on at the time of the failure, that's all right, right? As long as the metadata is in a consistent state. The other thing, of course, is that while it's possible to reconstruct the file system metadata in a lot of cases by doing what I talked about before, where I scan the whole disk, there's no way to reconstruct the contents of the file. If you were writing a certain number of bytes into the file and they were in the cache when the system crashed, I have no idea what those were, right? So even if I touch every block on the disk, I still can't reconstruct the contents of the files that might have been lost during the crash, whereas in a lot of cases, I can reconstruct the metadata. Yeah, so there were some early journal approaches that actually journaled the data blocks themselves, which you can imagine is kind of sad because now every data block gets written twice, both to the journal and to the file. Most of the time you just don't do that. All right, any questions about journaling? Journaling is an approach that I suspect you can see how it generalizes to other types of systems. The big idea here is that I represent some change I'm going, some complex change I'm going to make to a bigger system in one place that I can change easily. And then if I get stuck in the middle, I have something to look at to try to figure out what I was gonna do. So this happens in databases, this happens to distributed systems. This idea comes up in a lot of other places. I don't know if it came up here first, but it certainly is a very big part of file system design, even within just one disk. And you can imagine if I was doing some sort of transaction and Google's data center that involves five different machines, this idea is very useful because one of the machines fails or whatever, I can kind of figure out what I was doing and make sure that everything is up to date. All right, questions about caching and consistency? Yeah. Yeah, good question. So the journal will create more disk traffic. That is undeniable, yeah. There are, I'm trying to remember, there are ways to cache parts of the journal as long as the cache understands that the journal entries have to be written out before any of the changes that are on disk, right? So that's a normal requirement, is the entry has to be in the journal before I start making changes to the disk. So you can cache those, you have the same trade-offs you have with other caching operations, right? It's possible that the contents are lost. You know, when you get into the world of IO, you get into weird stuff, right? People have, you know, reliability and fault tolerance and the ability to prop a system back up are important enough that people have thrown a lot of fancy ideas at this problem. So for example, you have servers, well, well first of all, I mean what's the most basic solution to solving a certain category of the types of failures that would cause problems for the file system? What's the simplest thing I can do? Yeah, what's that? Eh, even simpler than replication. Cheaper and simpler than replication. Yeah. No, you guys are thinking, like think around the machine. Like what can I do in the data center to prevent a certain category of these errors? Make sure the power doesn't go out. I'm serious, you guys are giggling, but like every data center needs to have a UPS on site, right? And a lot of the big ones have backup generators on all sorts of other fancy power supply systems and a lot of power cleaning. You thought the power that you got on the grid was good enough for these computers, no way, right? They have all this complicated processing to keep the power lines very stable. Yeah, so that's step one, is just don't let the power grow out. Then I'm okay. Then as long as some moron doesn't come and like punch my computer in the face, I'm okay. I can handle a lot of different types of failures, right? The things people brought up, replication, you have these fancy server hard drives that have battery-backed caches, just in case somehow the power goes out, they have an actual battery on them that allows them to finish writing things to the drive before they shut off, blah, blah, blah, right? So replication is certainly a big one too.  I have two and a half copies of everything in, if you really look into heart, if you wanna spend a couple of fun hours, start looking into, and you would think this would be an easy question to answer, look up how to reliably store data for like five or 10 years. Cheaply, this is not a solved problem. You can spend a lot of money to have someone do this for you, but if you have like huge amounts of photographs or other videos and you actually want them to survive for a while, you think, oh, I'll just put it on a USB stick, nope. Those only last a couple of years, blah, blah, blah. So, I mean, storage is hard. But there's a lot of exotic solutions out there because storage is also really useful. Okay, so let's talk about FFS. Now we have to time travel back into 1982. How many people were born in 1982? Okay, yeah, I think it's me and Ron. Yeah, so old, right? This was included in the first BSD release in 1982, and to some degree, I think, you know, FFS and BSD grew up together, right? BSD was one of the first really effective and popular distributions of Unix, and it brought FFS along with it. There's a guy named Kirk McHusick who has been essentially the FFS developer now for, I don't know, forever. He's still working on sort of modern variants of FFS the last time I checked, and the whole file system was pretty much built by him. I'm certain that other people have contributed by this point, but it was pretty impressive. So there is something, there is a, FFS is still in use under a different guise, or something called the Unix file system. Has anyone ever used UFS? I've never used it. I don't know, maybe it's a BSD thing. Anyway, so UFS is still out there, still being actively maintained has, you can imagine after 20, 30, 34 years, there's a lot, has a lot of cool features, has a lot of modern features, but still something that people use. So, FFS is kind of an interesting beast because FFS, if you look at the system as a whole, there's a certain set of contributions that FFS made to file system design that have been really lasting. And then there's others that are kind of things that we got rid of as soon as we could, because they were really tied to a real deep integration with the geometry of disks at the time. And those were the ones, those were the features that kind of didn't survive. Partly because disk geometry, I mean disks have gotten faster, flash makes geometry irrelevant. And to some degree, some of the geometrical stuff that FFS did will sort of blow your mind, but it's certainly not relevant anymore. But pretty cool that, and this is kind of a neat example of somebody really making a deep and careful study of a particular piece of hardware and designing a system that really, was really tightly coupled to it. So imagine that you have, take the disk that we talked about and make everything slower. It spins slower, the heads move really slowly, there's not really much data on it. What are some of the different types of challenges that you might want to tackle with that drive? Remember, you are, as a file system, you are creating a on-disk data structure to hold information. So on certain systems, you can just pretend that every disk block is the same as every other disk block. Once you get to a really slow disk, what are some of the things that you might want to keep in mind? Or the things that you might want to try to do? Or these features of disk geometry that you might want to exploit? Yeah. Okay, so that's an interesting point. This is a, Sean Briggs have a good question. Why is the outside of the disk a better place to put things that are accessed more often? Yeah. It's not quite correct. I mean, the head was moving laterally, right? The tracks are an equal distance apart pretty much on the entire disk, I think. What's different about the outside of the disk? Yeah. So okay, so that's a great point. The track, the data density is constant. So the track at the very outside is where it's the longest, which means you can store more data there. So that's good, but what else does it mean? Yeah, I mean, this is basic physics, right? The disk is rotating at a constant speed. So the head is passing over every part on the disk and every in one rotation. The inner tracks are shorter, meaning that there's less information on them. And that means the bandwidth from the inner tracks is smaller. Does that make sense? In one rotation, I see more data on the outside and so I can pick up, I can write more information, but I can also read and write information faster because there's more going under the head. And so do you guys remember that video with the, no, you might have noticed that most of that activity was happening at the outer edge of the disk. It was, you know, you didn't really see it spending a lot of time close to the inner part and that's because all, well again, I hate to be categorical about things, but all same modern file systems start allocating it at the outer edge of the disk and work inward because, you know, you hope that you don't have to use the inner parts. Did you have a question? So, but, you know, and all this is sort of based on layout, right? So this goes back to the things that we were talking about before. So where do I put common data structures that I could access all the time, like I notes? Here's the other thing to keep in mind and this is a big difference. I should have said this before, but this is a big difference between FFS and LFS. What else is true in 1982? Right. Yeah, okay, so the drives are smaller, the data density is lower, everything's slower, but what else is true about this system? There's another part of the system that's really critical here to file system performance. That's also changed quite a bit since then. Yeah, the buses were slower, that's okay. What's that? No, what's the, I mean, what's the other, we just spent, you know, a couple of lectures talking about using something else to make the file system faster. What was that? Memory. So these systems had a lot, lot less memory. Now, you know, memory has also sort of been, been subject to Moore's law and so that today I suspect the ratio of memory to file system size is probably different than it was back then. We had less memory, less memory for caches and so remember what we were saying about file systems like CXD4, kind of, maybe it doesn't matter as much where you put the inodes because the cache is gonna soak up a lot of your access to inodes. On a system in 1982, not true, right? I have to worry about where the inodes are on disk because my cache is not very big and I'm gonna spend a lot of time finding the inodes and potentially operating on them. And then you think about things like the relationships between files. So from a completely probabilistic aspect, if I touch a particular block in a particular file, what's the likelihood that I will next get a request for some other part of the file? And to some degree, you might argue that the probability is uniform over the entire file system. It's not quite true and there are certain cases where I can get away with some clever optimizations. If I can observe certain patterns of file access. All right, so let's talk about some of the common features that FFS, we'll come back to the rotational planning but let's come talk about some of the things that introduced that you guys are familiar with. So FFS introduced sort of a modern large block size, happens to coincide with the page size. So FFS introduced the idea of trying to do contiguous block allocation on disk. This is important because things that are contiguous on disk are close to each other on disk. And so you can get those things more easily without having to move the heads around a lot. FFS introduced a bunch of features, symbolic links.  Symbolic links, file locking, file name links. It could be not maybe not as long as you wanted but long enough not to matter and things like quotas for shaled file systems. So these were all features that FFS introduced that are pretty much standard operating procedure now. All right, so what's close on disk? So there's two, on the disk that remember, go back to our geometry stuff, there were two things that were slow. What are the two things that prevent things from being close on disk? If I'm in one, well I mean another way to think about it if I'm in one spot on the disk and I want to go to another, there's two things I have to do. What are they? Well they're both physical movement, right? There's two types of physical movement. So I need to move the head, so my head is moving laterally and then I need to do what? Yeah, wait for things to come under the head. So I need to wait for the disk to spin. Now over time the seek times have really, I think this is another one of these ratios that's changed over time. The seek times moving laterally have not changed very much and I think also as the tracks have gotten smaller I suspect that it's gotten harder to center the heads over a specific track. Remember, not only am I flying over to one other side of the disk as fast as possible, well once I'm there, I have to make sure that I'm in the exact right spot where I have a head that's, I have a track that's as small as possible because the smaller the track, the more data I can put on the disk. So I think that's probably kept seek times from improving to the same degree. Now again, you would probably be happier with the disk that had a slightly slower seek time in exchange for 10 times more capacity. That's probably the trade-off that we've made. So here's some ideas that I've best introduced in this space. So one is this idea of a cylinder group. A cylinder group is all of the data on every platter of the disk that I can read without moving the head very far. And it's not without moving the head at all. It's just without moving the head very far. So on each cylinder group, FFS creates almost like a mini copy of the file system. So it creates a backup copy of the super block. Remember the super block has all this metadata about the file system itself. This is something that it's used to have multiple copies of because if I lose it, the file system is toast. So I create a copy on every cylinder group. I create a cylinder-specific header that has information about that cylinder group that's kind of similar to what you would have on the file system super block. I create the iNode table and then a number of data blocks. Does anyone remember what this looks similar to? What does this remind you of? What's that? Somebody's mumbling something back here. No. What other file, I mean we looked at a file system before. These are EXT4 groups, right? Remember EXT4 had these groups like zero, one, two and each one of them had iNodes, data blocks. I mean this is kind of where this idea came from. And this is almost like I've created, taken one file system and on each cylinder group, I'm creating a mini file system. The advantage to doing this, particularly in 1982, is that it really ensures that things are close to each other. The data blocks in the cylinder group are linked to the iNodes within that cylinder group and so that sort of guarantees that I can read the contents of a file without leaving the same cylinder group and therefore I don't have to move the head very far. Ah, there we go. It's like it's own little mini file system. So yeah, so this is like EXT4 groups. We saw this before. So, and this is where, this is kind of the stuff, FFS stuff that will sort of just blow your mind, right? So the super block that FFS used, it would actually do some profiling of the disk and we used it to do this really detailed rotational planning. So this is not a problem that we have anymore because bus speeds have improved but it turned out that at the time, you could, the buses, so somebody brought this up before and it's a great point, the old buses that connected the disks with the rest of the system were not fast enough to read or write data at the full speed that it could be read or written from the disk. Does that make sense? So I can sit there on a platter and I can pick up data at some rate but I can't get it over the bus to the rest of the system at that speed, okay? So what does that mean? It means I can't actually read consecutive disk blocks. I might be able to read a few until the cache on the disk fills up but if I have a big file, if I start reading it consecutively, zero, one, two, three, consecutive sectors on the disk, at some point I'm gonna have to stall and wait for the data to get to the system, the rest of the system into memory and then pick up things again. Why is this a problem? Like, what makes this particularly unpleasant? Let's say I start off and I get zero, one, two, three and then I'm, I can't read four yet because the cache is full, what do I have to do? Well, I know I want four next but then what do I have to do? Let's say I can't read four yet, yeah. No, the buffer's full at this point. Yeah, Ron's got it. I need to go all the way around again, right? So I got zero, one, two, I'm ready for three but I can't fit three into my cache so, you know, like, and, you know, these disks weren't spinning as fast as they are now so now I've wasted this whole rotation waiting for three. So FMS, I'm giggling, this is just so awesome, right? FMS would actually measure this and it would lay out files like this. It would say, okay, well, I know that I can't read things this fast so rather than allocating, you know, block sequentially for the file, I'll make sure I allocate them with these gaps in between that allows me to read the file sequentially, all right? And this is one of those things that just makes you think like, I don't know, I don't know what to say, all right? I'm happy disks aren't like this anymore but on the other hand, if this is what you're given this is what you have to do, right? I mean, sometimes engineers have to make things that are kind of nasty, all right?  And if not, why not, right? And this is a good thing. So one thing I'll point out is FFS and a lot of these early systems dealt with low level hardware interfaces that were on some level a little less clever than they are now. Someone came up to me after class, maybe a month ago was talking about, there are new, I think there was a question on the midterm about voltage scaling and frequency scaling for processors. There are CPUs that are coming out right now that actually do this for you. So they think that they're smart enough where if you provide them with a workload they're actually going to choose when to speed up and when to slow down automatically. And to some degree, this has happened on a variety of different types of pieces of hardware. Discs are not immune for this. So, you know, for three, four, five decades now both hardware and both sort of software people and hardware people have felt a sense of responsibility about solving this particular problem. How do we make IO fast? The problem is that some of these solutions end up making things difficult for the other part of the equation. I mean, this is a hardware software problem. You're not going to make it go away but how do you expose information and whose responsibility is it to do things, right? In general, the trade off here which is sort of ubiquitous to computing is that you can make a piece of hardware that is very, very good at doing one particular thing and it can do that thing extremely quickly. It really doesn't matter what it is. At some level there are certain software approaches that don't work well when you try to implement them in hardware but that's usually because you need too much hardware. Most things, I can make a chip that does that one thing way, way, way fast and then you will ever implement it on a general purpose process, right? On the other hand, software is super flexible. It's easy to update but it is always going to lose a performance back. So today I would argue that things have, my take on this is that things have shifted very much in the direction of software. Why is that? Why do you feel, you know, why would you make an argument that software is what is our problem at this point? Yeah, okay. Well, I guess we're worried about, a little bit worried about that. So maybe some of the hardware gains aren't, but what's happened? I mean, okay, well remember though, this is a trade-off here between performance and flexibility. So hardware allows you to say, you know what, in exchange for lack of flexibility I am going to gain really impressive performance. Why might things be leaning in one direction or another today? 2016, yeah. Okay, that's fair. I mean, people have different needs. What else? What's happened over the last 50 years? What's that? We need to create more problems for software engineers because we have more of them. I like that. Not sure that's completely, don't tell anyone else that. It's not quite what I'm thinking.  Just so fast already. To some degree, find your computer engineer buddy and give them a big pat on the back because they did a great job. They gave us these things that are so powerful. We have no idea what to do with them. That's the problem now. The problem isn't like, oh no, my smart phone's not fast enough. I just don't think that's really a problem. And if it is, software is probably the culprit. So to some degree, you could argue, even if Moore's law is starting to flatten out a little bit, Moore's law happened over a period of multiple decades. And the rest of us, people who write software, I would argue that I think computers could, probably getting in trouble for saying this, but I think that if we had a decade where computers didn't improve in performance at all, nothing, just zero, no new chips, nothing faster, whatever, just we're stuck with the same hardware we're still with today, we could solve a lot of problems with that hardware. We don't need new hardware to solve a lot of the problems that we have. So anyway, there's my little rant. Let's talk about how this works at the disk level and how this can sort of frustrate some of the things that FFS was trying to do and that will be done for today. So all the rotational planning that FFS was doing relied on the disk obeying the geometry assumptions that FFS was trying to make. So if the things that FFS thought were close on disk, weren't close on disk, this becomes a problem, right? So here's one way of saying this, right? This allows, so this was sort of the early model of disks. You had a map from sectors and you can pretty much map that directly to where things were on disk. And tools in systems like FFS exploited this to do clever things, right? The advantage of this is that it provides the OS with a lot of visibility and you can write pieces of software like FFS that rely on this information.  I mean, give them credit. Hardware does, if your processor rebooted as many times as your OS does, you would be mad. Hardware just can't fail in the same way. So here's another approach which is, and to some degree this happens already today, where, remember I said before that modern disks have these huge performance variations even with the same model, modern disks can take a sector that's failed and remap it to another part of the disk. What this means is that assumptions that the file system is trying to make about where things are on disk get broken. So I thought that these two blocks were right next to each other because they're consecutively numbered. But it turns out that the disk has remaped one of them way to the edge of the drive and now every time I hit my I know table I'm doing these huge seeks. It's not good. And pushing more complexity into the device, to some degree the device is closer to the little firmware that runs on the device is closer to the hardware and can optimize performance better in certain cases. The problem here is that the operating system that's up doing dumb things. So a friend of mine about a decade ago looked, he did this interesting study where he looked at the performance of certain file system designs on RAID, which is a system that we're gonna talk about on later in the week. And what he found out is that the file system designs were trying to do these things that were clever that were based on on-disk layout. So again, they were based on assumptions about locality. When the underlying disk breaks those assumptions, not only are they not helpful, but they actually are harmful. So it turns out that just, he wrote this paper about it that was called stupid file systems are better because the idea was these clever things that the file system was doing to try to optimize performance were actually causing performance degradation. Okay, so I will just wrap up on FFS. I'll put these slides online. You don't need to see this material. We will start on LFS, log searcher file systems on Wednesday.


Sailors and Marines assigned to the amphibious transport dock ship pre-commissioning unit Arlington are preparing the ship for its commissioning. Petty Officer John Buxton shared the significance that the ship's journey and milestones hold for him. It's a culmination of all of our time and efforts that we've spent accepting orders here almost two years ago and finally get to see this come to fruition is one of the greatest experiences of my life to see the blessings of the crew and the fitness and the happiness of all of us all together. Watch as her crew brings Arlington to life live on Saturday on Navy.mil, direct to Sailor and the Pentagon Channel. From the Defense Media Activity, I'm Petty Officer Amara Timberlake.


One of the biggest misconceptions in the history of histories is the common misunderstanding that pyramids were built as tombs for the pharaohs when in actual fact no mummified remains have ever been found in any of the pyramids of Egypt. The idea probably spawned from the fact that the Giza pyramids are situated in what is now a large funerary complex that was added during the dynastic period of Egypt and the discovery of an inscription in the great pyramid by Richard Weiss appeared to confirm this though in the 21st century carbon dates on the inscription have yielded results that suggest it was from the 19th century and possibly added by Weiss or his team however even more recently this has again been dismissed and some researchers have proven that this inscription may be dating to the time of King Khufu of whom the great pyramid is attributed the inscription translates as the friends of Khufu gang to use this translation suggests that locals helped a workforce funded by Khufu to enter the great pyramid for whatever reason and some researchers have shown later additions to the great pyramid and in particular the queen's chamber what do you guys think about this anyway comments below and as always thank you for watching