Hi. Hello. We are Play Nitride and welcome to our booth. Please introduce yourself. Yeah. My name is Serena. I'm the marketing team member. And hi. Hi. I'm Falcon. I'm leading the marketing division and welcome to our booth. Cool. This is a huge display. What's happening here? Oh yes. Yes. You can see here this. Actually we have three kinds of different microd solutions. And one of them is pixel-line matrix. This is pixel-line matrix technology. We transfer microdichip onto the PCB backplane and use this way to tile into any kinds of large signage board in any aspect ratio and the customized displays. And like here you can see. This one is 166. This is the modular display. And here's the resolution and the pixel page is 0.833. And we use 324 pieces to tile it. Actually we have different kinds of solutions like 0.43 mm, 0.75 mm. That's all can be customized. Nice. Yeah. And you can see the contrast ratio is really good because for microd display the advantage is to be such a large signage board the black ratio can up to 98%. So the contrast ratio is really good and also the brightness. It can over 2,000 nits easily. Nice. Yeah. That's awesome. So what's happening here? Yeah. Okay. And this is the AR application. This is the second solution for us. You can see there this is the panel microd display here. There's a panel there. Yeah. This is the SPAIC. It's 4,536 ppi. You can see it's full color, full HD resolution and the brightness is really really high. So you get a full HD and a half inch. Yeah. Yeah. Only 0.49. And it's very bright. How bright does it get? It can be around 150k. 150k nits. Yeah. Is it full color? Yeah. Full color. And you have to put this in front. Yeah. Because it's too bright. Yeah. And protect my camera. Yes. And this two module is made by this display. We embedded the microd display here as the light engine as the light resource. And it can light to the wave guy and reflect back to your eyes. So you got a wave guy going on? Yeah. The wave guy is from our partners, but sorry we cannot disclose. But you can see these two modules, there's a little bit different. This one is one dimension pupil expansion and the other is two dimension. All right. This one is two dimensions. Let's go jump in here. This is the state. The FOV is 48. And you can see the FOV is wider. It's a wider field of view. Yeah. Wider field of view. I'm trying to focus on the other. It's not really easy to take a picture. Yeah. I found it. Yeah. Huge. Huge display. How's the quality of the full color? Quality. You can do... There are the specs, huh? Yeah. Yeah. Here's the specs. Is it mass production? Yeah. Yeah. Of course. It's already mass production? No. Not really, but we have sold to several customers for their evaluation. Evaluation is cool. But I want to see millions. Everybody should buy it, right? Yeah. How far in the future is that? In the future. We will say soon. Soon. But please give us a little more time. We are working on it. All right. Is this the best micro display demonstration? I won't say best. Because they still have some space to work on, to be better. There's always have a way to go better. Nice. Yeah. It'd be interesting to see some awesome applications come out of this. Yes. Yes. Maybe AR, the AR future. Yeah. So please follow us. We will be better and better. All right. Yeah. And also this way you can see this is our... You can take the video like this. You can see. Wow. It seems to be invisible display. Wow. Think about in the future. The display will be invisible. So there's a transparent display. Yeah. Yeah. Transparent. Another display. Yeah. So there are so many different kinds of applications you can imagine in the future. Hey. Shark. Yeah. Shark. Wow. It will jump to the front screen. All right. 1960 by 1480. Also sell to customers. So you've been busy the last three years, right? Yes. Just a lot of things happening. Yes. So many things come to small volume mass production. And also like this way you can see the transparent display and with touch function. And you can see here the ambient light is so bright. But you can still see clear picture of our display. You can see here. I showcased the animation here. But you can still see the background. You can still see the decoration. And that's only because it's micro LED and it's very bright or? Yeah. That's so bright. It can be 1000 nits easily. And even the peak high is 3000 nits. What do you say? 33? Oh 3000 nits. 3000 nits. Yeah. The peak high can be that high. Nice. Oh. Okay. And you can see this one. This is a high earring transparent display. You can see the no matter the color, the brightness or the controversial. It's so good. This is our latest version. And we are going to use it as to go to mass production. Nice. Mass production. How soon? We are going to. This is pretty close. Pretty close. We are doing now. All right. Let me go around here. Yeah. And also here. Oh, let me, they are there. Okay. This is a wall of wearable watch. Yeah. And micro LED smartwatch. Yeah. Yeah. Yeah. And not only we can produce, we have the technology, not only RGB, also quantum dots. So some of the watches is made by quantum dot technology. So you can see it's HDR. So HDR micro LED smartwatch. Yes. You can see the spec here. If I wear this, I'll be the, I'll be the star of the show. The smartwatch is big. Yeah. 256, 256. Yeah. 24 bit. Yeah. Just to get even nicer colors. Yes. The color gamma is 120. And one thing I guess is maybe it's going to allow for extra brightness compared to other smartwatches. Yeah. Yeah. Yeah. The brightness can up to 4,000 needs the peak high. Nice. Yeah. And also you can see here, we can, you can get closer to already display. This is also be tiled. I always like what you just take the video. This is, that one is that kind of blue watering waterfall, starring waterfall. And this one is another peach size, it's 0.75 mm. And you can see closer, it's almost seamless. And the contrast ratio is really high, almost unlimited. And the color and the brightness, that's all perfect. Nice. And here you can see, the display can be any kind of different type, even like a cube. Wow. And it can be like a figure to put your maybe several images, photo album into this kind of cube. I want the cube like this. Yeah. So a lot of your technology is coming to mass production, mass market. Yes. What is a challenge to bring something to mass production? Yeah. It needs huge factory. Yeah, I think that for the production, it takes time, step by step. Because in the beginning, it's a new technology. So when we start, just like already before, so the beginning time at the beginning stage, everything may be expensive because there's, it's not with a lowland scale. And so that's why the first micro D product will be the TV with very luxury TV. After that, because it's start production, then we can get better experience for the yield and also make the volume become bigger. With a bigger volume, the cost will be reduced. And then you can penetrate to other market. So we are also talking to the automotive and wearable. And in the future, we'll go for the other applications like signage or also maybe for the monitor and even go for the mobile devices. When you make a huge factory, do you need to partner with or who's going to make it? Okay. How do you make it? Who's going to wear and where is going to make it? Okay. So Serena already introduced that there are different using different background technology, PCB, TAT, silicon. So the business model will be different. So for PCB, maybe we'll have to do the business by ourselves and we can sell either the PCB module or we can sell the whole system. It depends on our customer's requirement. And for TAT, that needs the TFT makers, their help. So we work with TFT makers to produce for the TFTs, for example, like transparent displays and also others like wearable displays using TFT-based technology. And then for silicon-based technology, then that also works with partners. They design the design house, design the background and play nitride. We do the transfer, make the microad, transfer onto this display and make this tiny display with very high resolutions and then to our customer to make the real AR glasses. So for example, I get one comment here. It says, can those play nitride microad displays work in something like RUZIX glasses? So potentially it could be some partner this or that that could make end product and hopefully soon that people can buy. Yes. As I said, the first TV, microad TV from Samsung, it's already, they are already selling in the market. Of course, that may be the price is high. And then I think AUO already announced they will have shipped the microad wearable devices to their customer. And this year, you can buy a watch, a microad watch. And then for the automotive, because everyone knows automotive takes longer time for verification because we need to make sure the safety and everything to, so this takes longer time. But we believe like 2026, 2027, then you can have a car with microad display. There's a comment that says that transparent display is good for automotive application. Yeah, actually that's the first, the demo when we bring to these car makers, they get very interested in this technology. So it's very good. Of course, we know there's already in the windshield or the window, there's it's transparent, but there's not no display there. So of course, this is one of the idea to use the micro transparent display a microad. In the future, as I know for the in the future, it will be the autopilot cars and the whole the interior design copy design will be different. So transparent can help them to enable other ideas to maybe in like five years later, the car will all look different. In five years, I want to call an Uber where I can decide to pay without ads. And if I if I want to have a free ride, boom, they'll be advertising on my window the whole way, but it'll be for free. Maybe, but it depends. I don't like ads. So maybe, yeah, maybe you can choose and also some entertainment and also maybe the car looks like the more like in the movie night like so if you don't pay for the Uber, there's ads. But if you pay for it, you can watch Netflix. You can watch whatever you want. Yeah, that sounds better for me. So you make it ready. I'm just talking. I'm just a YouTuber, but you can work with a car company. Did you come here and say, okay, the car is coming in 2026 and we want to have three million pieces? Yeah, that's we're working now. So but maybe, yeah, but maybe not three million in the beginning because that they were for the car makers, they were introduced a new technology for their higher model first and then penetrate to all the models. So maybe everyone can have this kind of the cars design within 10 years or say 20, maybe it's the 2030. At that time, most of car need to become the EV car. So then combined with micro ID together, micro ID also can help to saving the power. So it's good for the EV cars also. I love this late week. It's the coolest conference and all these displays are so amazing. But I don't want to wait 10 years. I want to have these stuff like, you know, one or two years is okay. Is it okay if I say that? Is there any way to speed things up? Maybe somebody comes and say, I have a lot of money. I don't know what to do with it. Like that's great. Oh, I can bring this to market one year. Yeah, because now there's no, as I said, the scale is not enough.  So we need to sell you very expensive for our materials vendors or equipment vendors. And then so more like it's more like a volant or say chicken and egg.  But it cannot start very soon in the beginning. So of course, if there's someone who has a lot of money and then he can afford it to speed up this, maybe two years, then everyone can have micro already. That's also my hope. Some of these companies over there are very, very big. I'm talking Samsung, LG, BOE and all that. What is your role? How big you're going to be?  Do people come here? The specialists who are here, do they come to play nitride and say, oh, you're the best.  Sure. For the micro ID, we're the leader. And I can say the most, I think some of the booths, their demonstration, the micro ID is from Plain Nitride. And also the transfer is made by Plain Nitride. So we are the leading company for the micro ID, including the chip and also the transfer, all the technology of micro ID. And we are not sure if we become a giant in the future or not. It depends on the market change and all the positions for everyone. But we want to be the best technology provider for micro ID and to give everyone the best viewing experience. The way you transfer is that the future, or there's some people suggesting different ways to do? Still, there's lots of different transfer technologies. But for us, we won't say only one transfer technology is the best because, for example, to transfer the micro display is 4,500 ppi. You need one kind of transfer technology. And for PCB and for TFT, the big plan and also the pixel density, they are all different. So we will use different mass transfer technologies for different back plan or different applications. And the Quantum Dot, it's a great partnership to have? Yeah, we have very good partners who help us to build up using the Quantum Dot color conversion. So Quantum Dot is also a solution for micro ID because the Quantum Dot can provide even better color gamut and also it can help to help some of the red color micro IDs because the micro ID red is using one kind of material and green and blue is another material category. So for us, if with two different materials, it may also take more time for the process and the integrations. So Quantum Dot can help some of the technology. And also for the micro displays, very tiny displays, Quantum Dot also plays a very important role. So we can have one small display to become full color. Is there printing? Well, it depends on the pixel density because printing, there are some limitations. So we can use printing or photolithography, just depends on the displays, pixel density. So you can work with that too? Yes. All right. So you are compatible with many companies here. You're working with them? Yeah. And they're talking with you? Yes. So we think, oh, everyone is our partner and we want everyone to join to develop micro ID so maybe it can help to grow the micro ID business very fast. Not just one company, pretty nice, right? Yes. We believe we work very hard for micro ID and we believe we are the best for the technologies. But it's just a small company. If we want to make micro ID affordable for everyone, I believe everyone should join to work for the micro ID. How expensive is it to make low volume four by three aspect ratio displays for retrovaming of those micro ID displays compared to LCD, which is stock on 16 by 9? Wow, that's a very specific question. It's hard to answer right now, but we just give you a reference, the Samsung, the wall micro ID TV, it's roughly 100 inch and the price is about $100,000. Okay, $100,000, but you're talking about some huge, huge micro ID. Yes. I was just talking about a little micro ID for video game machine or something. I'm not sure. Yeah, but I just want to say it's kind of expensive now. So we don't know what will be the real price for that kind of spec. You need to be real to do the feasibility and do the real details calculations, but it will be much higher than LCD right now. But for our roadmap, we will drop the cost 50% year to year. So why 50% cost reduction? All right. So in five, six years, it will be nearly free. I'm talking it will be cheaper, hopefully. Yeah, hopefully. And how about the somebody's asking 0.43 millimeter micro ID can scale to TV size? Yes, of course. Actually, our demonstration was TV two years ago. But unfortunately, that demonstration only in Taiwan. So at 0.43, the pitch actually is the same as 75 inch 4K. So we just need more modules and tied into a bigger size. So it's already the TV's pixel pitch. So you're working with the Americans, with the Koreans and the Chinese? We work with worldwide, everyone in the world who is working for the display or who are interested in the display, no matter the panel makers, the camera makers, or the different system makers, everyone. And one thing I like to always kind of figure out is because there's eight billions of people in the world, and not everybody's so lucky to have $100,000 for it. But how soon is it possible that micro LED will maybe help to make things cheaper? Like, you know, affordable for everybody in the world? It depends on the ecosystem. For us, of course, we hope it can be very soon. But depends on like panel makers, depends on these brands, how fast they introduce these technologies. Because as I said, increase the volume, increase this kind of market size, the cost can be lower. Just like how we see the LCD in the beginning, several years, it grows very slowly. But someday, just boom, the cold LCD costs drop super fast, and everyone's joined. And then more and more people can be affordable. That's what happens for LCD. So micro LED, if you want to do the same thing happen, I believe more and more people or more companies joined, that can help. Cool. All right. Thanks a lot. Thank you. Thanks very much to ZXS to be one of my sponsors here at the Display Week 2023. ZXS is based in Shenzhen. And I will be doing a video very soon with them, featuring their transparent displays, OLED, LCD light box, ads machine. So thanks a lot. I did video with them nearly 10 years ago when they were doing tablets. And now they do these cool devices. Thanks a lot for watching. Check them out.


I used to believe this lie that I couldn't talk about racial justice because I'm white. The confusion there was that I am probably wrong about racial justice because I'm white. But that doesn't mean I can't be broken open or turned inside out. There is nobody who lacks the right or authority to speak out against injustice. Anyone of us can turn our preaching up the hill. Anyone of us can speak truth to power instead of morality tales to the suffering. Anyone of us can choose to preach a more just kind of justice.


All right, good afternoon. Hopefully, quiz three went okay. Looks so far that looking at it went okay-ish. I don't know when the TAs are meeting to market, but I will update you as soon as I know any more information. So today we're gonna be a bit more modern. We're gonna talk about SSDs, which people actually have in their machines, and RAID, which is a fun topic. So SSDs or solved state drives are more modern than hard disk drives. There's no mechanical parts. They're kind of like RAM, they use transistors and to store data rather than magnetic disks so you can't actually ruin it with a magnet. So pros, no moving parts or other physical limitations where the spinning actually matters or actually waiting for something to physically move. It's gonna be higher throughput. It's got good random access so everything doesn't have to be sequential. Like we saw with spinning disk, if we didn't access it sequentially, our performance went down by like two orders of magnitude. They're more energy efficient, again, because we're not spinning a hunk of metal. Better space density so we can fit more bits of information in a smaller space, but they're gonna be more expensive. They're gonna have lower endurance so solved state devices actually have a limited number of times that you can write to them and then after that they wear out and you can no longer write to them anymore. So there is a level that they will just kind of wear out and you won't be able to use them anymore. And as we'll see based off just how they're made and their architecture, they're also more complicated to write drivers for. So this is the architecture of an SSD and what it looks like for the purposes for us. We don't really have to care about the dye in the yellow and the plain in the brown. We only have to care about blocks and pages so blocks aren't exactly what we talked about before so a block in this for a solved state device or drive is a group of pages. So all the pages luckily are usually four kilobytes which actually matches up to our virtual memory pages which is nice. The not nice thing is that they are organized in blocks and there are special rules for reading and writing them. So SSDs use like NAND flash. They're gonna be much faster in hard drives. Page size will typically be four kilobytes like I said and then it's gonna be about an order of magnitude quicker than a hard drive so reading a page would be like 10 microseconds. Writing a page would be 100 microseconds and then curiously, erasing a block is one millisecond and you will actually note here that it is impossible to erase a page so I can only erase blocks which is why actually writing drivers for this are kind of complicated and your kernel actually has to handle these specially in order for it to work correctly. Yep, so in this, so in the next slide we'll see that when you write you're only allowed to write once after it's erased and then after that it's locked until you erase it again so you still have to erase it. So yeah, this is where that comes in so if you actually program and write drivers for these things then you have to use pages and blocks so the rules are you can only read complete pages so they have to be written to you can't just read and initialize stuff and you have to only write to freshly erased pages so you can't rewrite over something without doing an erase in between and erasing is only done at the block level and a block will typically have like 128 or 256 pages and yeah the entire thing needs to be erased before you can do even one write operation so that is why writing would be slow so if you want to modify one page that has already been written to well you're going to have to the naive thing to do would be to copy all the other like 127 pages on that block to a new freshly erased block and then write that modified page to that block and then update all the information so it points to the new block instead of the old block so you're going to have to do lots of writes if you just want to modify a single page so the OS can help with this a little bit or the kernel so SSDs will need to garbage collect yeah sorry well that's what you have to do but if you want to just modify a single page you don't want to just write out 126 of them or 127 of them just to write out one so we'll see we can do something slightly better yeah the naive thing to do if you want to write something new is you have a freshly erased block you transfer all of it to a new block and then erase the old block and then you have to update everything so we'll see that so the SSD will need to have to garbage collect some blocks so like move any pages that are still so in that worst case I was talking about where we have to move 127 blocks or pages sorry that would of course be the worst case so the kernel one smarter thing to do instead of moving all 127 it could just move the blocks that it knows are actually still in use so that would still be some overhead but it's at least more intelligent and we're not just writing you know n minus one n minus one so the disk controller also needs some help to indicate what blocks are alive so even if you have you know you use the block you've written to it the SSD is going to assume that that block is in use even if the kernel no longer uses any of those pages anymore so the kernel needs some way to talk to a disk and tell it that hey that block has all the pages I'm no longer using so you can go ahead you can erase it at your will so I can write to it again later so that's what that trim command is so if you've ever seen that it's mostly it was an issue when SSDs were new and not every kernel actually took SSDs into account but now pretty much everything is going to have it so the trim command is basically the kernel informing the SSD that I'm not actually using any pages on this block you're free to garbage collect it and erase it and then the SSD hardware whenever it would be idle can just go ahead and erase it in the background whenever it's not doing anything else terribly important so that's the long and short of SSDs we won't go into too much detail about them just really know that you have to deal with they have the special rules where you have to erase a block at a time blocks contain multiple pages and you can only write to a freshly erased page and that's about it and then yeah so so far we've been talking about single devices so I guess mockingly this is just sometimes called a single large expensive disk or S LED and you can tell by the kind of wording of it that it might not be such a great idea so it's just one big large disk so the naive thing to do again is if I run out of space for all my files well I just go buy another hard drive and transfer everything to the new hard drive and just start using that but the drawback of that one it's going to be slightly expensive as you try and get more density and also it is a single point of failure so if you lose data if that disk dies then all your data is gone so what people typically use is something called an array or a redundant array of independent disks and it's basically just data is distributed across multiple disks and you can when you do that you can give a whole bunch of different trade offs whether you want to trade off performance or redundancy in case one of the drive fails and how many failures you actually want to endure so one of the first RAID configurations you might see is something called RAID 0 has anyone ever used RAID before? probably not, one, okay so this is a term if you're like a data hoarder or if you really want good performance you would use something like this so RAID 0 is also called a stripe volume and all that means is all the data is just put together in kind of larger chunks and then those chunks are distributed over the disk so in this example say file A was made up of eight chunks well the odd number chunks would go on the first disk which would be disk 0 and the even number chunks would go on the second disk which would be disk 1 so now whatever I need to read a file well I can read half from disk 0 and then half from disk 1 and it's going to be twice as fast and then similarly if I need to modify it assuming I'm modifying something that's big enough well instead of writing all that information to one disk I write half the information to one disk and then the other half of the information to the other disk so your reads improve by a factor of how many disks you have and so do your writes so you can do the same idea with more and more drives so you could do this with three drives, four drives, five drives but the big drawback is that if any of those drives die then you lose data because you only have one copy of everything and no way to get it back so instead of being a single point of failure for one disk now you have multiple points of failure which is kind of bad if you actually care about the data so it's really only for performance only all the data is just striped or basically just split into chunks and put on multiple disks so you're going to have faster parallel access you're going to get roughly end times of speed up for both reading and writing but any disk that fails is going to result in data loss you've way more points of failure so one you've end points of failure for how many disks you have and only takes one so the kind of opposite approach to that where you essentially make an exact copy of everything is called RAID 1 and that makes each disk a exact mirror of each other so if that file now is just four chunks well if all four chunks are on disk 0 then all four chunks are also on disk 1 so now if any of those disk drives die then I still have a backup and you can do this for multiple drives so I could have four drives that are all the same or five drives so this is where the textbook terminology also gets weird so we'll discuss at the end something called RAID 10 or RAID 1 plus 0 the textbook when you expand RAID 1 it doesn't just assume every disk is an exact mirror of each other it goes into this weird alternate thing that we'll discuss later so just watch yourself if you're reading the textbook but so RAID 1 simple but pretty wasteful so every disk again is an exact copy of every other disk and this gives us way more reliability so as long as one disk remains we have no data loss because they're all the same so if I have four disks here that are all the same I could lose up to three of them because they're all the same so I can tolerate everything except one disk dying so it's going to have some good reliability that's a lot of points of failure that need to occur in order for you to have data loss and it's going to have good read performance because it doesn't just have to read from one disk it can split up the reads across multiple disks and in this example say there were four well one disk could you know send a1 one disk could send a2 one disk could send a3 one disk could send a4 so you could split up the reads across the disk but you couldn't split up the writes so it'll have good read performance but the write performance will be the same because you have to write the data to all the disks and it might actually be a bit slower if you kind of run out bandwidth so yeah yeah because if I'm writing say I have like four disks in this case if I modify something in a1 I have to write it to every single disk in this case yeah so you're yeah so you're assuming the bottleneck is actually writing to the device so if I write to four devices at the same time it's the same as writing to one so that's why I said assume that you know we have enough bandwidth yeah yeah well you'd issue all the same commands to all the disks so ideally all the disks would pretty much be the same like manufacturer and everything so they'd all behave the same so you just send the same commands to all of them no so these would be independent disks so so like disk 0 and disk 1 would be two separate hard drives they're separate yeah yeah so there's multiple platters so that's just the only way to access data on a platter so one head per platter but you can only no no yeah in this case these are separate so in this disk 0 and disk 1 they could be a hard drive they could be an SSD they could be whatever yeah you can buy a bunch of SSDs and configure them like this if you want you can configure a bunch of hard drives like this if you want typically if you do this you really only care about as much data as possible so like if you care about your day you go to the store you buy a bunch of spinning disks and you set them up like this so if you care about if what SSDs will fail too right so if you care about your data you might want that or you might want the performance if you want SSDs so if I you know I could do RAID 0 and get twice the performance as my single SSD I just buy another one yeah yeah so the idea yeah the idea of RAID is like in its name the redundant array of independent disks so everything's independent and then you configure them however you want so we've seen two configurations so there's RAID 0 which is like go as fast as possible I don't care if one fails I'll take some data loss and then one is like as safe as possible everything's a copy so you can think of this as like it's one way to think of this is it's like automatically creating a backup for you so anything that you you modify your lab it's saved on two devices so now if one dies and the other one you know still has your data you don't lose your lab or anything like that okay so then the idea here comes for RAID 4 which I'm just here for illustration it's not actually used but the idea is key here yeah question is where two and three go so two and three were large mistakes they didn't they didn't work that well so we'll skip over two and three we'll be skipping over four because four basically doesn't exist either because it's a bad idea but we'll see this is how things work people get an idea same thing redundant array of independent disks so the numbers just corresponds to how they're configured so arrayed four so does kind of what RAID 0 was doing where it stripes the data across disks but instead of here there's one disk dedicated to parity and what that will do is basically store some information such that if one of the disks dies then it can actually reconstruct what that bit was so easiest way to argue about it is with bits so we can see something like this so say we had I don't know that's like three bits of information and then we had four drives so in this case we actually I'll call it three so this three is going to be our parity drive and it's going to essentially be an XOR of everything so let's say across these disks we're storing one zero one we're storing zero one zero then we're storing one one one so the idea here is we have sorry we're getting there so this is our data across our four disks and we're going to use yeah data across our three disks and we're going to use the last disk to store some information such that we could recreate the information if a disk dies so disks three in this case we'll store parity information will be an XOR of all the bits four disks here I'm just saying there's three bits across all the machines so I'm just illustrating just because I don't want to write out like a full byte so in this case so on this so for bit three so on this zero one and two well the XOR between three things is basically the shortcut way to think about is it's going to be zero if the sum of all them are odd or it's going to be one if the sum of all them is sorry it's going to be zero if the sum of all them is even and then one if the sum of all them is odd so in this case if we add one plus zero plus one well that's even so the XOR of all that is going to be zero so we would store that information on the third disk and then for the next bit we have zero one and zero so that all together is odd so that would be a one indicating it's odd and then for the last one we have one plus one plus one so that's three so that's odd so if we XORed all of them that would be one so yeah so this one would yeah so so this is what would have sorry it was your question so the hardware will say it fails or like the kernel will try and write to it and it won't actually be written to or it won't respond anymore or something yeah well if the parity just disagrees then something there's probably been a failure well then that's okay yeah so that's a good question if the parity disk fails well the parity disk fails you throw in another disk and recalculate the parodies for everything you have to trust the hardware that it actually says it if it works it works so these devices will say whether or not they work yeah yeah so that's a good question so if I say everything was working fine if I go ahead and modify you know information on disk one then I'm going to have to modify the update the parity bit on disk three and then similarly if I change anything on disk zero I also have to update the parity information on disk three and if I update anything on two I also have to update disk three so yeah so there's going to be some concurrency issues here right yeah yeah that's what that's what we're doing yeah that's what we're going to do okay so that's what we're going to do so this is the reconstruction so let's assume disk zero dies so disk zero is now dead so just remember it was one zero one but not using that information we can get that back so disk one zero is now dead so now it's dead all the bits are gone so ideally what you do here is you buy a new disk and then stick it in and then you can recreate the the failed disk zero and copy it to a new disk so we can use this parity information to keep track in order to recalculate it so we have an unknown here so it's like unknown plus zero plus one is reading the parity bit is even so I need either a one or a zero added to one to make it even so I need a one right so the bit three is definitely a one in order to jive with the parity bit there and then for bit two well I have a one plus zero and then plus an unknown and that has to be odd so the only number it could be is a zero knowing that parity bit and then similarly for the last one I have an unknown plus one plus one so like unknown plus two and then that has to be odd so if two plus some unknown is odd well that unknown has to be one if it can either be a one or a zero so just knowing what was on disk three here that parity information knowing it's an XOR we're able to recreate our one we're able to recreate the data on disk zero yeah I'm just showing you by one bit but if you do this times eight it's a byte add five columns yeah so yeah yeah well so if you're dealing with the hardware so this is like at the bit level but you'd be loading it in into like a page or something like that and then writing it back out in page so you just issue commands to the disk and let the disk figure it out so in this too so you're you can miss mix and match disk so you typically it'll be as slow as the slowest disk so if they're all from the same manufacturer they'll probably all behave the same so you won't have a bottleneck but if you gave it like you know three SSDs and one hard drive well then it's going to be as slow as the hard drive essentially all right so that is the idea behind the parity calculation but as we kind of discussed this is not great because if you modify anything on any of the disk even if I was to only modify you know a1 on disk 0 b2 on disk 1 and c3 on disk 2 well one block on each of those disks would correspond to I have to update the parity information on disk 3 so it's going to do three times the number of writes as the other one so it's going to be very disproportionate and you're going to get bottlenecked by that parity disk but that's why it's not used and I'm only using it to illustrate but with parity so you can use essentially all the space minus the space from one of the disks and you need at least three drives to do this type of you need at least three drives to do RAID 4 so we can get n minus 1 times performance because all the rest of the data is striped and that's essentially just just arguing that we ignore the parity disk and then it's essentially like RAID 0 but then the con is that that's not actually going to be true because your write performance is really going to suffer because any update has to write to the parity disk but the other pro is we can tolerate a single disk failure with good performance and not wasting that much space so but if two disks fail then we're screwed so RAID 5 is the actual is how RAID 4 is actually used so RAID 5 is exactly like RAID 4 the only difference is there's not a parity disk it distributes all the parity information across all the disks so now before disk 3 had the parity calculation for A, B, C, and D well now disk 3 only has a parity calculation for A 2 is the calculation for B 1 has the calculation for C and 0 has the calculation for D so you're hoping that since you distributed across that you'll kind of even out across all the disks that have to update the parity information so this is the first RAID 5 or RAID 5 is like the first one that's actually used aside from 0 and 1 so 4 is not actually used because it's going to be really uneven on that parity disk so RAID 5 is basically just an improved RAID 4 all the same pros as RAID 4 except it doesn't have that con where we have probably suffering white performance because we're bottlenecked on a drive so 6 is like RAID 5 except there is now two parity bits so instead of before where our parity bit was called P before now we have another parity bit called Q and then like with RAID 5 to RAID 4 we're not going to have two disks that just calculate parity bits for P and Q we're going to distribute them across all the disks so your first parity calculation for P would be a simple XOR if you're interested in the calculation for Q or the second one that is where your linear algebra courses come into play and I won't go over the details it like somewhat involves a Galois field so if you don't know what that is you can learn later but you have to do some more complicated math if you want to get a second parity bit there so from a usage point of view all you really care about is do the extra parity I essentially lose another disk of space and again I needed these four disks to do a RAID 6 and also the right performance is going to be slightly less than RAID 5 because I have another parity calculation and also one thing that's listed on here that is a big drawback too is you might actually care about reconstruction time of how long it actually takes to you know make the new disk a copy of what it is replacing so like when I was doing grad school I had a RAID 5 array I was doing my work one of my drives died and I was like yeah that's okay all my data is fine and I can tolerate one drive failure but sure enough you buy hard drives together they tend to fail together so after about a month another one failed and then I lost data so you want to replace them when they start failing they're expensive they're still expensive yeah the school is to buy them yeah drive space isn't free yeah what's SSD because I don't even think let's see quick google search yeah they don't even make 12 terabyte SSDs you can buy a 12 I just bought a 12 terabyte hard drive can't buy a 12 terabyte SSD well you can except they're going to be like several thousand dollars so no I had no in grad school it was less than that is more I cared about my stuff not getting deleted so I had a RAID and then it died so replace your stuff because they tend to fail together so another sorry yeah well so it was RAID 5 so it was like this so one of the disks died which is fine you can still use it because you have you can calculate all the information on the fly so you can still access all your files and everything so I was like yeah this is fine I can still work because because it takes like days to rebuild it as well to recalculate the parity for like I forget how big they were like they were probably like four terabytes so it might take like four days to rebuild it yeah on the new disk so here if you have four disks and one dies you have three disks so you replace the old one you put in the new one and then you have four again that has to reconstruct all the information that was on the one that died to the new one well two died I didn't get to the reconstructing step yeah one died and then I'm like yeah this is fine and two died yeah so that's what it's good to know this in actuality two died but one was like just dying because as soon as two died I ran to the store and bought a new one and I it was just starting to die so I actually got most of the information off it so it like gimped along yeah yeah this is like assuming disk drive they can fail in fairly spectacular ways so like the spinning magnetic disk one spectacular way they can fail is called a head crash where that magnetic head hits the platter and makes essentially makes it explode and you're not going to retrieve any data off that because it is now in a billion pieces yeah yeah it becomes a slow rate zero so so if one of these disk dies say I don't have a three anymore right in a normal a zero if I just had you know if I just had normal parity or normal rate zero I would have like a one a two and a three and then I could read them all but if I have this and say this two dies well if I want to get a three back I have to kind of calculate it back so it's going to yeah so it's going to be a calculation step so it's going to actually perform a little bit slower if you have one dead the pen yeah but remember like the parity is going to be distributed across and most of them will probably have the information but you're still going to have some parity so it'll be slower if one's dead ideally you don't do what I do and you go replace it so in this case if just zero died yeah yeah so you would lose all of it but you can recreate the parity bit because all the other information's still there okay so another thing you could do too is something called so there's another raid one that is a combination of two that's in the textbook so you can also have something called a raid 10 or sometimes it's called raid one plus zero and the idea behind that is that it stripes but it has two copies of everything so say we have disc zero disc one disc two so I'm going to use six discs to illustrate this this three disc actually I'll put it to the side so the idea behind this is for half the disc you do what raid zero does and you just completely stripe the information so for example I would have like a zero a one a two and then I could have you know the next bits of that file a three a four and a five so within those three discs they're all striped so this is essentially exactly like raid zero and then the one plus zero is I make a copy of all that with the other disc so this way in this dimension it's kind of like a raid one so disc three is an exact copy of disc one or sorry disc three is an exact copy of disc zero disc one is an exact copy of disc four and then disc five and the exact copy of disc two so that way now I get pretty good performance and also if one of the disc dry if one of the disc dies so say disc zero dies this disc is dead well the cost of recreating it is going to be much faster because there's no calculations involved I just take out disc zero I put in a new disc and it is an exact copy of disc three and only disc three so you just have to copy all the data from one disc to another disc there's no calculations across disc involve or anything like that so instead of my scenario where it would have taken days to reconstruct it only takes you know hours to just cut straight copy a drive especially if they're a spinning disc you just copy it all sequentially and it will be quite fast so now the question for you too is in this configuration whoops I hit that in this configuration how many drive failures can I withstand before I actually start losing information and losing information in this case means that I have one of these blocks where I don't have any copies anymore or if I parody I don't have any means to reconstruct it anymore so this has no parody so you can essentially argue about that I don't have any copies of a block left so we got two two minimal yeah yeah so ever no so so my worst case is if I lose two discs I'm I might be screwed by if I'm lucky I could lose up to three in this scenario so why is that so now let's assume disc three dies so disc three is dead so if disc three is dead well essentially I'm my danger zone if you want to think of it that way is I only can't lose disc zero because now on this zero that's my only copy of a zero and a three but I could lose any other disc because there's two copies of everything else so if I lose this disc I'm screwed I lost you know a third of my data and it's no longer there but I could lose any other disc so I could lose disc one so now we're in a bit more of a danger zone so I lost disc one so now I'm essentially if another disc fails I'm essentially at assuming everything's like perfectly you know randomly distributed or uniformly distributed I'm at a 50-50 shot now so if I assume disc zero four or two or five could die next well if disc zero dies well I'm screwed because now I don't have a zero or a three if disc four dies I don't have a one or a four anymore but either disc two or disc five could die so if one of those dies then that's fine and I still have all the data but now I don't have any backup copies of anything else so because there's mirrors of everything so if I lose both mirrors I'm done but I can you know if I have at least if I have one failure in every stripe that's fine I can go with that so this is going to extend up to like if I have eight discs I can tolerate my minimum two failures because you're still no matter how many you have if both pairs die then you're screwed but I have more pairs so I could if I'm really lucky tolerate four failures if I have eight discs for example yeah so if I have four if I have four or sorry if I have eight discs it is yeah it would essentially be like two more here yeah so because they're mirrors so the app if you got really lucky the most amount of failures you could tolerate is the number of discs divide by two but your minimum is always two because you could knock out the other mirror so it depends kind of how lucky you think you are but the nice thing about this is to reconstruct it again it's really really quick because I don't have to do any computation or anything like that but of course if I have one of the big drawbacks though is essentially I'm wasting half the space just for the mirror so the more discs I have with raid five and raid six the more space I get back like closer to the theoretical max if they were all in raid zero but in this your capacity is always going to be half yeah yeah so the question is could I draw do really reliable ones for half the mirror and then uh unreliable ones for the other half that are cheaper I imagine you could there's more exotic file systems if you really care that can do a bit better than do the parody a lot faster and typically you're at that point you're wasting your money on really reliable drives you just you'd be better served just to buy more yeah so so the question is how long does it take a disc to fail um so I mean it's just there's a distribution of failures within like off the top of my head I mean it really depends on what drive you buy and who makes it but like the average failure rate for two years ballpark probably like five percent something like that so if you are google and you have you know thousands and thousands and thousands of drives you're going to be somewhere in that distribution and a lot like like five percent are going to die within two years yeah so I've had drives of yeah I've been lucky some drives have lasted you know eight years they still work like 12 years who knows the drives that died on me they were like it was like warranty time plus two months so I think it was like they died after like a year in two months so I got unlucky that was a notoriously bad batch and now I just don't buy drives from that manufacturer anymore sorry let me turn this off now let's see all right so more options for persistence so we saw SSDs and RAID SSDs more like RAM except you know accesses and page and the only differences in blocks and because of this block thing where you need to you know erase it and you can only write to a freshly erased block and you can only erase groups of pages the kernel and the SSD kind of have to work together using something like trim and we saw RAID to tolerate failures and improve performance using multiple disks so that's it for today and just remember I'm pulling for you we're all in this together


Hello, and welcome to this Getting Started video. This video is about how to get started with ST's X-Cube VS4A software on STM32F7 microcontrollers, which will enable you to connect to Alexa. For more information about Alexa in general, you should check out Amazon's official webpage. The X-Cube VS4A STM32Cube expansion package consists of libraries and application examples for the STM32F7 series microcontrollers acting as Alexa-enabled devices. And it runs on the 32F769i Discovery board, which provides a native Ethernet interface. X-Cube AVS key features are an ST Microelectronics framework for the Alexa voice service, AVS-oriented STM32 applications, a ready-to-run smart speaker firmware example, TCP-IP connectivity, replaceable basic audio acquisition, the AVS protocol encapsulation, and an example of a limited audio player. Now, let's use an example embedded in the X-Cube VS4A and working on 32F769i Discovery board. On this board, you can find the main features needed for AVS, such as Ethernet, Lineout, or a microphone. Now, let's see how to run the software on our board. First, download the X-Cube VS4A software from the ST website at www.st.com.x-cube-vs4a address, sign up or log in, and get the software. Then, unzip the package and paste it at the following address. And finally, using the STM32Cube programmer, download the image to the target. On the STM32Cube programmer tool, click Connect. Select the .bin file, select STM32769i board, and start programming. Now the target is ready to use. On the Discovery board, connect the USB, Internet connection through your private network, and a speaker to hear Alexa. Normally, your board should be alive, and you can check if it has an IP address. The last thing to do is to connect the device to Alexa services. Open your favorite browser on your PC and type the IP address previously provided on the board. Connect to your Amazon account. It is important to note that in the address bar, STVS4A should be replaced by the IP address. And now, you are ready to speak to Alexa. Press the button to go to page 1. Press the user button and start to speak. Where is Chuck Norris? If Chuck Norris wants you to know where he is, he'll find you. If he doesn't, you won't know until it's too late. What is the time in Tokyo? The time in Tokyo is 5.59 p.m. What is the weather in New York? Right now in New York, United States, it's 56 degrees Fahrenheit with cloudy skies. Today's forecast has intermittent clouds, with a high of 68 degrees and a low of 52 degrees. Set an alarm at 7 a.m. Alarm set for 7 a.m.