So, look, to cloud is often the term you get thrown around with these sorts of things, so I'll move right along.  These are my opinions. These are related to the company I work for, but these are based heavily on the experience we've gathered doing, you know, providing services for a number of clients in the Moodle space as well as other IT experience. I'm going to throw some information out as well. I hope this information is useful. This is, you know, the aim is to sort of broadcast knowledge, but ultimately the decision around any kind of hosting change, because if you've got a Moodle, any change in terms of being internal versus external, it's a change, and you need to understand what the implications of that are and take some ownership and, you know, and sort of assess various options as there will be. So a little bit of a terminology cheat sheet. There's a lot of marketing speak. There always has been in the enterprise hosting game, right? In the hosting game, there's all sorts of sort of noise and various bits of metrics that may or may not be terribly relevant. So Cloud, I like this one as someone else's computer, you know? So not the one that you're holding in your hand, which is probably a phone, or the one that's under your desk, which of course, Cloud providers like Amazon will argue with that that it's not at all, but to some degree it is, right? You don't know where it is, you just know it's a computer. You know, an internal hosting put simply as a machine that you at least know which room it's in, and if you've got the right sort of pass card, you can walk up and actually touch it, and you can turn it off and on, and you might have the responsibility to actually fix it, like, you know, put new disks in it or replace it or call the manufacturer based on a warranty fix. So dedicated versus shared, you know, I think that's pretty obvious. Shared clusters are where you have lots of moodles sort of hosted together. Moodle, this is the context of the discussion, as opposed to sort of one physical machine or one cluster hosting one big Moodle. On-prem to me, it just means internal. Virtualize would probably be the way that if you are running internal infrastructure, most people are probably running virtualize at this point in time, the arguments for bare metal stuff fewer and fewer, and, like, hybrid, to me, that's just marketing speak. I mean, different people have got different ideas of what that even means, but it gets thrown around a lot in the current sort of cloud discussions along with terms like workload, right? So, you know, these things sometimes don't actually mean too much. So, as a Moodle, let's think about a Moodle as sort of almost a living thing. So, I'm a hosted Moodle, right? So, I'm a hosted Moodle either internally or externally.  You know, here's Kevin, he's the Moodle product owner. He sort of owns the product. He is in charge with the decisions and responsibilities around the platform. He is the one that the business sort of yells at when things go wrong or explains what the roadmap is or these sorts of things. And here's Barry from Australia. Here's Barry, the sys admin. So, you know, he cares about the environment. I mean, this is leaning more towards probably internal hosting setup, but there's someone who cares about the bear infrastructure. This might be an external vendor, but they care the systems up. They care that the disk doesn't fill all these sorts of things that, you know, everyone's had outages, right? That are related to these sorts of things. It happens. And here's Wayno, the Moodle developer. He fixes bugs. He works on the integration stuff. He writes some plugins. You know, he sort of contributes to core. And here's Sue, the support manager.  She's the one who answers the phone. She's the one who understands if people's passwords aren't working or there's some sort of integration problem.  So, thinking about that in terms of your Moodle is a good way to understand any kind of change in the hosting setup, how it will affect the people on that list. So, I'll just run through this recently quickly. Sort of a month in the life of a Moodle, right? You know, learn is learn. Teachers engage. You know, support team deals with students. You might do an upgrade. There might be some sort of issue that people triage. You know, there's some new plugins or modules get released. Okay, so just sort of the things that happen a day in the life of a Moodle. Once again, this is sort of almost a cheat sheet of the things you might need to understand when you're talking about, you're moving from one particular hosting to another. So, value points in Moodle hosting, okay? Now, please think about, like, because sometimes the metrics that sort of clients discuss are not necessarily things to focus on. So, I started off here with, and it doesn't matter whether we're talking about internal or external or cloud hosting, whatever. These things are still core to a Moodle that is a central part of your organization. So, the first thing I'll say there is Moodle Streetcred. Now, what I mean by that is, you know, essentially, is this provider a Moodle partner? Or do they know Moodle well? Have they engaged with the Moodle community? Do they really get Moodle, right? Because some providers will just say, oh, it's just a PHP application with MySQL, the Postgres, no worries, we can host that, we know what we're doing. But, you know, it matters that they understand what Moodle is, right? Like, you know, I'm not saying that's the only way to do it, but it is something to understand. Ask some questions, see what they've done. Please tell us, please convince us that you understand Moodle well, and obviously support the Moodle partnership network.  You want it to be there. You don't want it to be going up and down, right? Performance is important. Performance means pages load snappily.  Performance means that when you schedule a quiz at the same time that the site handles it, that the Moodle site handles it, you know, it is important. People are very used to using snappy interfaces. Like, you know, the masses out there, especially the younger generation, do not want to wait for a page to load.  So performance matters. Support processes, you know, really think about what the mechanics of getting support from either your internal responsibility team or your external team means. Like, what questions are you allowed to ask them? How many times can you ask these questions? You know, what are the promises around response times? Do you have to use a ticket system? You know, these sorts of, you cannot understand too much about these sorts of things because support is very easy to get wrong. Support is very easy to do badly, right? Like, you know, everyone's had engagements with internal infrastructure teams or whoever where it wasn't very good and you don't feel like you're being listened to and your problems don't get fixed. Flexibility as well, you know, you want to be able to, it's an open source system. Moodle was designed to be, was built to be flexed to be customized and optimized. So you should be able to push your Moodle in the direction you want to do. So just some reasons why you might want to host internally, right? And these are things that we see out there in the market. We need control, okay? We just want control. This is our organization. Great example, one of our clients, Victoria Police. Okay, so to them, the idea of, and to say to Victoria, to them the idea of having Moodle outside of their own infrastructure is just not feasible. It doesn't matter, you know, money, where, how, it just is not feasible for them to host their system outside of physical machines that they control. You know, so there might be on-site usage patterns that mean that you want to host internally. For example, a school, one of our schools in Sydney, they're reasonably remote and the internet connection outwards is not always that great. I mean, it's good, but it needs to be very big with the school of 1,000 people and the best guarantee of having Moodle available all the time is essentially on their land, right? So for them, it does make sense to be internally. You might have a very capable infrastructure team that just manages these responsibilities very well. Good, they're not all like that, as people will know. You know, you've got internal developer capacity, you have very complex and bespoke systems integration requirements where your Moodle is talking to a lot of other systems that are sort of on the same network and facilitating that externally is challenging. It can be done, of course, but it's challenging and it is a bottleneck to change. And simply, it ain't broke, right? Like if you're hosting internally well at the moment and it's working well and you're happy, then there isn't necessarily a huge argument to change. External hosting, you know, i.e. cloud in these days, sometimes it's just not feasible to host internally, right? You just don't have the skill set, you don't have the will. Sometimes there was a big mess of a Moodle. We've certainly been engaged by organisations where they made a big mess internally, you know, staff changes, poor decisions, whatever, these things happened and they pushed it externally as sort of part of the move. Like, we just want to get this off our plate. Sometimes Moodle outgrows the internal team. Sometimes they need the data center, they need the access that a data center and the internet, the data center provides as opposed to being internal. Corporate policy, let's push everything off site. You know, that's certainly a big noise in the university market in Australia at the moment. They want to get stuff off site, they want to get stuff off their infrastructure. Cost considerations, I mean costing internal, comparing the cost of internal versus external in reality is actually a bit of an accounting, it's a bit of accounting trickery as to how you cost these things in all honesty, but some people will make the argument that it's cheaper to be external, right? You may just have no willingness to take on more infrastructure. Now, I mentioned Cloud in the title and I'll sort of say clearly what I think is good, what we think is good about Cloud hosting, right? Cloud Moodle hosting makes sense for big sites where there's a lot of scalability and performance requirements of a reasonably hefty site. Okay, so we're talking sort of university level, hundreds of thousands of page views a day, big load spikes around particular time events, that sort of size, like you can still do that internally and we've got clients who do it, but it's start the arguments towards the flexibility and sort of capacity that Cloud gives you are reasonable and worth investigating. So a big Moodle with big usage footprint, it's worth thinking about what is this feasible or not and do you want to do it. Massive load spikes, the flexibility that Cloud-based AWS, for example, gives you in terms of just being able to double the size of your database when it's melting down on some huge period of heavy use. There is no way, I mean, sure, with VMware, you can sort of double the size of the machine but it's pretty nifty and it saved us on more than one occasion. It was a new capability. So if that's something that you have to think about in your Moodle, then maybe Cloud's something you should consider. But Cloud isn't a magic wand and if you want to move into a really proper Cloud architected solution, that may require investment and it may require rearchitecture and it may require solving other integration problems. It isn't just a matter of lift and shift. I mean, it may be but be prepared that with change come costs. So just want to throw out some problem signs in terms of your Moodle and some things that should make you think about whether or not your approach is perfect. Moodle version upgrade lag, common problem but you shouldn't be way behind versions of Moodle. There are so many tools and models that allow you to ease the pain of upgrades compared to back in the old days. We've earned a fair amount of money over the years doing Moodle upgrades for people but we don't see that as a sustainable revenue stream moving forward. We want our clients to be on the newest version of Moodle. We want to embrace continuous integration and automated upgrade processes because it's not good when Moodle uses upgrade shy because there's a lot of cool stuff coming out in new versions of Moodle. So you should be running on new versions of Moodle, right? I understand all the reasons why that's hard but you should be looking at ways to make yourself using newer versions of Moodle or liability. If your site has regularly got performance issues or is slow or is ropey, that's not good, right? That's not good. It's a core part of your infrastructure. Performance, same thing. Ask yourself the question in terms of application ownership. Ask yourself the question sometimes when you're doing a review, who owns Moodle? Some universities can't actually, well, in Australia, some universities can't actually accurately answer that question. They'll sort of point at various departments and people but someone, a single line of responsibility, right? And that's an important thing. It's someone who owns it, someone who can make decisions, someone who can drive things, someone who can veto things, you know? It's hard sometimes inside large bureaucratic organizations but it's important.  In the modern world, they just shouldn't be a problem, right there. You either turn up the volume on what you've got or you change your approach. You should not have to negotiate with infrastructure people to get another terabyte of storage. You just shouldn't, right? That's not the way we live anymore. We certainly sometimes have to but you shouldn't, right? Take a deep breath. Lots of information, okay? That's sort of the information end. We're drawing to the end. What to do next? Think about your strategic plan, you know? Have a sit down, get some people in a room. You probably have to do it more than once. Where are we going? What are we doing? Right? What's the current state of play? Oops, missed the C on the bold there. What are our problems? Draw them on a board. Put them in a backlog, rate them. You know, what are the bits that we're not happy with? What are the priorities? Which are the most important ones to fix? You know, what options do we have organizationally? Can we hire someone if we make a business case for it? Can we find some money to go and talk to a vendor? You know, make use of Moodle consultants and getting them to come into your organization and provide you and propose things, propose solutions to them, right? But that doesn't cost you anything. Get someone in there and say, look, here are some of our problems, right? Help. Give us some options. How much do we have to spend or, you know, what can you offer us? Like, why not, right? Make use of their time. In those discussions, we're certainly more than happy to have, but we're not the only ones.  Think about who your potential partners and vendors are and there are plenty of them and there are plenty of good ones. One more thing about performance metrics. It's not, I'll just sort of fast forward to the end because I'm sort of getting low on time. Things like uptime, storage and bandwidth, they're way down the list, right? Way down the list. Really, uptime, anything over 99, like guess what, uptime, yes, the site's not allowed to go down, never. Right, 99.99, 99.5, 99, whatever. It just means that the site is not allowed to go down. It's actually much more valuable to understand what the escalation responsibilities are if there's an issue and the guarantees they're saying about when they're gonna call you back and how long, how quick it is before they're gonna resolve things, then uptime. But that's, that's all the time for. That's great. Well done. Front of the floor. Thanks very much. Thank you.


Okay, so many times you will encounter a scenario in which you know chain is there, okay, so when it is a chain, how you will take care of that particular scenario, it's a special case how to deal with a problem in which the chains are there, okay. What is chain? Chain, we are considering a chain which has distributed mass along the length, okay, mass is distributed, fine, so let's assume that you have this chain, the mass can be uniformly distributed or non-uniformly distributed, it depends on the scenario, so let's say this chain has mass m and it has a length of l, okay, so suppose this is the ground for which you are saying that gravitation potential energy is 0, okay, by the way, the work energy theorem that we have derived is not only valid for the small masses, it is valid for the bigger masses also, fine, like in the case of chain, it is valid here as well, but the problem which you will be facing here is to write potential energy and kinetic energy for the chain, okay, because this entire chain is not located at a particular location at a particular point, right, so since it is not located at a particular point when you write mgh as potential energy, you will not be sure what edge to take, whether to take edge from here, there or there, we are not sure about it, right, so that is the reason why we have taken the special case of chain here, okay, so my question here is, find out the total gravitation potential energy of the chain, ug is what, you need to derive it, okay, no Bharat, we do not know what is centre of mass, yes, you can assume the chain is just touching the ground, the hint is, take a small mass, let us take this mass is dm and this is dy, this dy is at a height of y, okay, so yes, mgh at, no but what m, mass of what, total chain, no, so potential energy of dm is what, see dm is a point mass, it is a very very small mass, it has a fixed location, so you can write down the potential energy of dm as du, which is equal to dm g into y, okay, now the total potential energy will be nothing but the integral of this, now the problem with integral of y dm or dm y is that both m and y, both are the variables, okay, so you need to write one in terms of others, then only you can integrate, right, so the width of this dm is dy, so total length l has a mass of m, so dy will have what mass, m by l which is mass per unit length into dy, okay, so this is equal to dm, so just substitute it here, you will get g times m by l y dy, now you can integrate u and mgl integral of y dy will come and this you can integrate from 0 to l, that is how the y coordinate is changing, so what you will get here is that mgl by 2, this is what you will get as potential energy, okay, so in case you have uniformly charged, sorry not charged uniformly distributed mass in the chain, okay, then all you have to do is to find out where the center of the chain is, okay, where the center of the chain is and find out what is the height of the center of the chain, okay and once you find out the location of the center of the chain, you just multiply that with m into g, so m into g into height of the center will give you the potential energy of the chain, fine, so we will learn the distributed mass in greater detail when we talk about the rigid body motion later on, but right now you can use it as a thumb rule if the chain is uniformly distributed mass, then the potential energy is just mg into h center of mass, getting it, any doubts, any doubts to write the potential energy of the chain, kindly message, all you have to do is to find out where the center of the chain is, then entire chain will behave as if it is a point mass located at where the center of the chain is located, here we have also integration part, so this is how we have integrated, we have got dmgdy, okay, we cannot integrate it right now because it has two variables, fine, so we first write dm in terms of dy so that there is only one variable y and then I can integrate changing y from 0 to l, okay, so I will get mg l by 2, fine, so you can also write this as mg into l by 2 and what is l by 2? l by 2 is the height of the center of the chain, fine, so the thumb rule is, thumb rule is write down if chain is straight, then mg into height of center of the chain will give you the potential energy of the chain, fine, you are assuming to be straight, okay, any doubts, yes or no, please message, they go for length l, total mass is m, okay, so for length dy, what is the mass, mass per unit length into dy, okay, that's how you have to apply, getting it, all right, so let us take up a small numerical on the chain itself and see how we can apply, what we have done till now is that we have defined the potential energy of the chain, okay, and that too for a special case where the chain is straight and if chain is not straight then we have to follow the integration procedure to find the total potential energy of the chain, okay, for example, if chain is placed on a hemisphere, if chain is placed on a hemisphere like this okay, then you cannot just find out the center of the chain and just, you know, write potential energy accordingly, what you have to do now is, first you have to assume some zero potential energy then take a small length of the chain, find out its potential energy and then integrate it through the length, okay, so that you learn when you take up questions like these, okay, so let's not learn it as a theory, so once you try out these questions, message me, then I can help you with this, okay, meanwhile let us take a question, suppose you have a table like this on the table, you have a chain placed with l by 4 length hanging, this is l by 4, total length of the chain is l, fine, mass of the chain is m only, okay, this is a smooth table, it's a smooth, fine, now what will happen, the chain will slowly slide down, okay, you need to find the velocity of the chain when the chain completely come out of the table, find out velocity of the chain when it comes out completely, so see with respect to kinetic energy, the chain is a straight forward case because the entire chain, if it is sliding will be moving with the same velocity, so you can directly write down half m into v square to be kinetic energy of the chain, where v is the velocity of the entire chain, so with respect to kinetic energy, there is no ambiguity, I have seen it, others, let us assume this to be zero potential energy, this is zero gravitation potential energy over here, okay, so if you break the chain into two parts, fine, 3l by 4 part has no potential energy, u is zero for 3l by 4 and for l by 4 potential energy is what initially minus of m by 4 which is the mass of the hanging part g into center of the hanging part l by 8, so initial potential energy will be equal to the potential energy of this part which is lying on the table which is zero plus potential energy of the hanging part, hanging part's mass is m by 4, okay and its center is lying below a distance of l by 8 from the level where you have assumed to be zero potential energy, okay, so u1 will be equal to mgl by 32, there is u1, okay, k1 is what, initial potential energy is zero, okay, u2 is what, u2 is when the entire chain comes down the table, that is minus of mg l by 2, if entire chain comes down the table then the center of mass will move down to a distance of l by 2, fine and k2 you can assume it to be half m into p square, all right and w is anyway zero, there is no other force other than gravity which is doing work for which you have considered the potential energy, so you can say zero is equal to u2 plus k2 that is minus mg l by 2 plus half m into v square then minus u1 plus k1 mg l by 32, okay, you just solve this equation you will get the velocity, okay, so like this there will be, you know, I can understand there is a discomfort in taking up the problem related to chain, so this you can only master when you, you know, try to look for the questions which involves the chain, are you getting it, so if you have any books just look at the questions that have that involves the chain in it, okay, don't just count the number of questions every day, number of questions what you have solved, you should also be on a lookout of some of the unique type of questions, fine, so try to get hold of at least five or six questions related to chain and solve it yourself, okay and in case you have any doubts feel free to get in touch, okay, so we'll take a small break now, we'll take a couple of minutes break right now it is 11, right now it is 11, oh 1150, we will meet at 12, okay, is it fine, okay, so guys let me tell you we have done enough so that you can crack any question from this particular chapter, now whatever we are learning are different scenarios, like if the chain is there what we'll do, if this is there what we'll do, right, so but with respect to the concept, okay, we have learned everything.


Okay, so let's see, this one, a formal charge problem, it says, what are the formal charges on the arrowed nitrogen and oxygen atoms in the following molecule? Okay, so when you look at this molecule, it's nitromethane. So for all the videos we've recorded so far, it gives that formal charge equation, okay? For me, that's not the easiest way to do it, okay? For me, you just really just count the electron, one, two, three, four, five, and then you can figure out whether it should be a plus one or a minus one or a neutral one, okay? So since we're looking at nitrogen and oxygen, and we're going to ask you a couple of questions about nitrogen and oxygen, so how many valence electrons does nitrogen have? Five. Five, it's supposed to have five, okay? So when we look around the nitrogen, if there's a bond around it, we count it as one electron. If there's any lone pair electrons like up here, we count those as one electron as well, okay? So when we do that, we've got one, two, three, four, okay? Because remember, we count these as one, because even though there's two electrons, it needs one of those bonds, one of those electrons is being used by this oxygen over here for its octet, okay? So one, two, three, four, so five, and we have four, so we're going to have a plus one, okay? So we needed five and we have four, so that's going to be a plus. And then we look over here, what about oxygen? How many valence electrons did we look at with the periodic tables today? We should have six, right? And same sort of thing, we count each electron as one and each bond is one, two. One, two, three, four, five, six. Does it have six? Yes, so it's going to be zero, okay? When we look at this opportunity here, how many does it have? One, two, help me out. One, two, three, four, five, six, seven. So what's the charge here? Negative one. Negative one, yeah. Does that make sense? Yeah. Okay, so when we go over here and we look at the arrow of atoms, that one's positive, that one's neutral. So any question on that? It makes sense, right? Just count one, two, three, four. It's so much harder when you do that bond formula, yeah. Any question? That's the structure, it's more stable. Why is it more stable than what? So you put a bond here, you're saying? Well, nitrogen, how many electrons can it have around it? No, that's how many valence electrons. How many nitrogen, how many can it have altogether? Eight. Eight, that's called the what? Octet. Octet rule. Okay, how many does it have already around it? Two, four, six, eight. So we can't put two more in there, it would be ten. That's a common thing that a lot of undergraduates like to do, is try to make atoms have a higher than, okay, octet. Any other questions? That's a good question.