Why I'm usually unnerved when modern SSDs die on us • Hacker News Board

Re: Why I'm usually unnerved when modern SSDs die on us

#151

Post by hueving » Tue, Dec 11, 2018, 8:47 PM UTC

loeg wrote: post #104

godzillabrennus wrote: post #99

Earlier quoted context omitted.

As someone that identified a bug in a Drobo firmware once and was offered a job on the spot I think the problem with attracting talent is two fold. The first problem is really two parts, not only is it rare to find people who have passion for storage related technologies but very few will gain exposure to these technologies to develop that passion. Kids don't routinely grow up with a SAN in the house. They do tend to…

I'm mostly curious because I work in a storage-adjacent field (NAS) for a BigCorp and the pay is pretty good, if not quite FAANG level. It's not a startup by any means, but I will easily become a multi-millionaire in a handful of years. I was curious about the other side of the fence.

What is a handful of years? That sounds like FAANG pay to me.

Re: Why I'm usually unnerved when modern SSDs die on us

#152

Post by 0db532a0 » Tue, Dec 11, 2018, 8:48 PM UTC

blattimwind wrote: post #134

blincoln wrote: post #47

Earlier quoted context omitted.

Why shouldn't it? Isn't it just hardware too? In a mechanical hard drive, there are moving parts which can wear out due to friction, etc. SSDs are solid-state, so it seems like at least theoretically, it should be possible to build one that keeps working for decades. e.g. I have solid-state hardware from the 70s and 80s which still functions. I've always been a little mystified as to why SSDs' data areas wear out for…

> I've seen lots of writeups of how wear-leveling works, etc., but never a good physical explanation of what is actually wearing out over time. SSDs are flash are basically EEPROMs. In an EEPROM one bit is stored in a dual-gate MOSFET. One Gate is a normal gate, the other is floating, i.e. it just is a small conductive island. The information is stored by (quite literally) shooting electrons through the insulation of…

The electrons aren't shot through the insulation. They end up in the floating gate by quantum tunneling. The insulation by its name is non-conductive, and must be so that the electrons stay put. The degradation happens through general thermal wear.

Re: Why I'm usually unnerved when modern SSDs die on us

#153

Post by anticensor » Tue, Dec 11, 2018, 8:50 PM UTC

soneil wrote: post #88

JohnFen wrote: post #30

It may be irrational, but I remain very distrustful of SSDs, in part for reasons like this. I use them occasionally as temporary storage, but I don't use them for anything that would cause me a headache if the drive died without warning. So far, my observation is that their lifespan is considerably shorter than spinning platter drives, and spinning platter drives typically give plenty of warning before actually dying…

I'm just distrustful of drives. All storage is essentially cache, and should be treated like it. I'm of the opinion that harddrives don't actually function, they just maintain the illusion while they wait for a more interesting moment to die.

Why do their motors move, then? For making noise?

Re: Why I'm usually unnerved when modern SSDs die on us

#154

Post by pkaye » Tue, Dec 11, 2018, 8:54 PM UTC

russdill wrote: post #109

pkaye wrote: post #91

I worked on SSD firmware for quite a long time and here is my perspective. Early flash used to fairly reliable with almost minimal error correction. However with increasing density, smaller processes and multi level cells, it has gone progressively less reliable and slower. Here are some of the things that we need to worry about: https://www.flashmemorysummit.com/English/Collaterals/Procee... To compensate for all th…

This is a bit of a misrepresentation. The only flash that never had ECC was NOR. Some embedded systems had NOR, but I'd be incredibly rare to find a consumer SSD with NOR. When designing a NAND memory product, you aim for some max allowed error rate. You choose the error correction algorithm based on that target. Error rates for NAND products are precisely what the designer intended. Because SSDs are so large and the…

I don't mean to imply NAND flash never had ECC. Just that the early flash had needed maybe 1-3 bits of ECC and I would never see an 1-bit error until maybe a few months of use. Things were a lot easier back then. Scrambling and read disturbs were not a issue until later on. All the things you suggest can be done. Just so many opportunities to screw up in the implementation despite the best efforts.

Re: Why I'm usually unnerved when modern SSDs die on us

#155

Post by Rinzler89 » Tue, Dec 11, 2018, 8:54 PM UTC

xyzzy_plugh wrote: post #101

loeg wrote: post #93

Earlier quoted context omitted.

Users and administrators almost certainly prefer a 20 minute IO latency over data corruption. Host operating systems should probably flag an IO as failed long before 20 minutes and then you know 1) nothing made it to disk and 2) have some chance to avoid introducing additional corruption, if e.g., the OS is smart enough to kick out the drive when this happens. > Another problem is that the job while rewarding is not…

Both, and usually significantly. Last I checked it was nearly twice as lucrative to be a Ruby-on-rails developer than an embedded engineer. Embedded also attracts a certain type of engineer, usually very smart and able to manage extreme complexity with attention to detail but at the cost of anything resembling readable, let alone maintainable, software. The fact that anything at all works in the modern world is amazi…

May I ask how did you manage to leave the embedded world and where did you go after? I'm asking since after investing 6 years into this field, which I love, and jumping a couple of companies I realized the market(Europe) is really bad for this gig. Not only is our work highly challenging it's also poorly paid while at the same time our CEO is crying to the local press they can't find devs(to work for peanuts) and is forced to look for them in Asia.

Re: Why I'm usually unnerved when modern SSDs die on us

#156

Post by oasisbob » Tue, Dec 11, 2018, 9:00 PM UTC

Waterluvian wrote: post #5

"When a HD died early, you could also imagine undetected manufacturing flaws that finally gave way. With SSDs, at least in theory that shouldn't happen" Why shouldn't it? Isn't it just hardware too? "With spinning HDs, drives might die abruptly but you could at least construct narratives about what could have happened to do that" Why can't you do the same with SSDs? It feels like the author's main complaint is the fr…

The post resonated with me because of a stupid bug I hit in a ca 2011 SSD. (Samsung?) After 100 power-on cycles, the drive would brick itself. Required a firmware update in time to avoid.

That defect doesn't strike me as being inherently related to SSD media, but really left a bad taste in my mouth with what might be going on in the development process to lead to such instability.

Re: Why I'm usually unnerved when modern SSDs die on us

#157

Post by pbhjpbhj » Tue, Dec 11, 2018, 9:01 PM UTC

sigstoat wrote: post #83

pbhjpbhj wrote: post #51

Earlier quoted context omitted.

On the subject of capacitor death. Is there a robotic device that can take in a circuit board and swap out all the [electrolytic] caps?

i've never seen or heard of an automated board rework system. thinking about the steps and things i've had to do to manually rework boards, your machine would need not only be able to apply force to pull parts off of boards without damaging the board, but also be prepared to restore pads / through holes to usable states after desoldering parts, before new ones could go back in. there's a reason companies don't repair…

I've done it myself, save restoring pads -- to me it's just the sort of fiddly, finnickety thing that it seems like robots sold be good at. And, they're not going to burn their fingers or run out of hands to hold things!

Re: Why I'm usually unnerved when modern SSDs die on us

#158

Post by AnIdiotOnTheNet » Tue, Dec 11, 2018, 9:11 PM UTC

zokier wrote: post #122

AnIdiotOnTheNet wrote: post #56

Earlier quoted context omitted.

> but SSDs are a perfect example of an entire computer that you attach to yours, and speak with through one of the (many) storage-oriented protocols. These days most of what we call a computer could be described this way. Even your compiled machine language is ultimately far more abstracted from what the processor actually does than it was on, say, a 6502.

> Even your compiled machine language is ultimately far more abstracted from what the processor actually does than it was on, say, a 6502 Funny that you bring up 6502; that reminds me of 1541 disk drive for C64, which had mostly same 6502 as the host computer (albeit running at slower speed).

Most disk drives of the time were like that. One of the reasons the Apple II disk drive was so affordable is that Woz just used the Apple II's own 6502 to handle the grunt work, with their disk drive being little more than a drive mechanism, a PROM, and some ICs. Since this is The Woz we're talking about, he went ahead and broke with conventional encoding while he was at it and instead implemented a scheme which allowed for a few extra sectors per track.

It might be an interesting exercise to see how many peripherals are connected to your PC right now that have much more computing power than an 1Mhz 6502.

Re: Why I'm usually unnerved when modern SSDs die on us

#159

Post by ptman » Tue, Dec 11, 2018, 9:13 PM UTC

undersuit wrote: post #123

yzmtf2008 wrote: post #118

Earlier quoted context omitted.

Modern SSDs have incredibly large caches. For example, HP EX920, which is a TLC (triple layer cell) SSD, in its 1TB model contains a whooping 200GB of SLC (single layer cell) cache. It's entirely possible that your changes are simply in cache only, and hasn't been committed to the actual storage.

I don't know if I'm getting exactly what you're saying, but a sudden power off isn't going to wipe your SSD's SLC cache like it would do the DRAM cache on more expensive drives.

It's probably more like the superblock not being updated to point to the newest data. Instead it points to old data that hasn't been garbage collected.

Re: Why I'm usually unnerved when modern SSDs die on us

#160

Post by loeg » Tue, Dec 11, 2018, 9:21 PM UTC

Misdicorl wrote: post #114

loeg wrote: post #96

Earlier quoted context omitted.

Disk platters rotating at 7200 rpm are both perfectly smooth and perfectly aligned. The read head is something like a jumbo jet flying a handful of feet above the (perfectly smooth) ground. It's really crazy how close these things are, moving very fast. And why accelerometers are a significant feature.[0] > Can you provide some references? Wikipedia claims[1]: > In 2011, the flying height in modern drives was a few n…

The claim was hundreds of picometers, which is an order of magnitude smaller than a few nanometers. Literally nothing can be perfectly flat, nor perfectly aligned.

The 3nm figure is from 2011. 0.9nm, or 900 picometers, is maybe not an unreasonable progression from 3nm in 7 years. And — it's perfectly flat relative to everything else involved.