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Unpowered SSDs slowly lose data

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Re: Unpowered SSDs slowly lose data

#331

Post by orbital-decay »

lizknope wrote: post #258

I've been hearing about this for years and it makes sense theoretically but has anyone ever actually seen it? What are the errors reported? Or does the drive return bad data but reports no error? There was a guy on reddit that took about 20 cheap USB flash drives and checked 1 every 6 months. I think after 3 years nothing was bad yet. I've copied OS ISO images to USB flash drives and I know they sat for at least 2 ye…

Of course. Cheap USB sticks in particular "spoil" pretty frequently due to firmware corruption while being stored in a drawer, this is something they're known for since the invention. I had this happen with a few. For some designs, it's possible to reflash them and they'll work again.

Re: Unpowered SSDs slowly lose data

#332

Post by nirui »

nirui wrote: post #118
cobertos wrote: post #115

How does one keep an SSD powered without actually mounting it or working with it? I have backups on SSDs and old drives I would like to keep somewhat live. Should I pop them in an old server? Is there an appliance that just supplies power? Is there a self-hosted thing I can monitor disks which I have 0 access usage for and don't want connected to anything but want to keep "live"

The simplest trick is just don't use SSD for long term backup, use a normal magnetic hard drive instead, those thing way lasts _longer_ (but not forever, even in human timescale). I have a HDD that was 17+ years since it last powered on. I dug it out recently to re-establish some memories, and discovered that it still reads. But of course you need to take care of them well, put them in an Anti-Static Bag or something…

> thing way lasts _longer_

Sometimes I come back to my old post and feel the "What The Fuck" in all cap.

When I was typing that, my brain jumped ahead thinking maybe I should also tell the fact that the data don't actually last forever, which distracted me and there you go, "way lasts longer" instead of "lasts way longer".

Re: Unpowered SSDs slowly lose data

#333

Post by dusted »

This is true, but it is generally true. Even for UV-EPROMs the retention time can be as low as a 25 years, if kept warm, even with the window sealed correctly. Magnetic drives are quite a lot better, around 50 years.

CD-RWs are somewhat wider in their stability, I have ~20 year old discs that are becoming unreadable because the actual foil is delaminating from the plastic disc. Meanwhile I have ~40 year old DS-DD floppies that are still fully readable even though their medium is in physical contact with the read/write heads (although here, again, storage conditions and especially the different brands/batches seem to make a difference).

Re: Unpowered SSDs slowly lose data

#334

Post by lazide »

coldtea wrote: post #330
lazide wrote: post #327

Earlier quoted context omitted.

So not enumerating as a drive, and not allowing you to read even valid blocks is ‘working’?

Yes, same as a facility self-destructing, if it was programmed to do so, is working as per its spec.

And what spec requires that? I have yet to see one.

Re: Unpowered SSDs slowly lose data

#337

Post by fsckboy »

spoaceman7777 wrote: post #141
fsckboy wrote: post #123

Earlier quoted context omitted.

this is about drives that are not plugged in. are you saying parity would let you simply detect that the data had gone bad? increasing the number of drives would increase the decay rate, more possibilities for a first one to expire. if your parity drive expired first, you would think you had errors when you didn't yet.

No, I'm talking about parity raid (raidz1/z2/z3, or, more familiarly, raid 5 and 6). In a raidz1, you save one of the n drives' worth of space to store parity data. As long as you don't lose that same piece of data on more than one drive, you can reconstruct it when it's brought back online. And, since the odds of losing the same piece of data on more than one drive is much lower than the odds of losing any piece of…

but this article is about unpowered ssds, those that are not in service but being kept for the data that is on them, as a type of back up copy. they could represent an entire raid set.

Re: Unpowered SSDs slowly lose data

#339

Post by spoaceman7777 »

danparsonson wrote: post #148
spoaceman7777 wrote: post #140

Earlier quoted context omitted.

Yes, but different pieces of data. The stored parity allows you to reconstruct any piece of data as long as it is only lost on one of the drives (in the single parity scenario). The odds of losing the same piece of data on multiple drives is much lower than losing any piece of data at all.

But the data is not disappearing, it's corrupted - so how do you know which bits are good and which are not?

checksums

Re: Unpowered SSDs slowly lose data

#340

Post by danparsonson »

spoaceman7777 wrote: post #339
danparsonson wrote: post #148

Earlier quoted context omitted.

But the data is not disappearing, it's corrupted - so how do you know which bits are good and which are not?

checksums

Where are you storing your checksums? If the answer is 'on the corrupted drive' then what makes you think that the checksums are correct?
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