>unpowered SSDs slowly lose data
so it's as if the data... rusts, a little bit at a time
Unpowered SSDs slowly lose data
121–130 of 341 posts
Re: Unpowered SSDs slowly lose data
#122A solution I haven't yet seen in this thread is to buy multiple drives, and sacrifice the capacity of one of those drives to maintain single parity via a raidz1 configuration with zfs. (raidz2 or raidz3 are likely better, as you can guard against full drive failures as well, but you'd need to increase the number of drives' capacity that you're using for parity.) zfs in these filesystem-specific parity-raid implementa…
How would this work? Wouldn't all these drives start loosing data at roughly at the same time?
Re: Unpowered SSDs slowly lose data
#123A solution I haven't yet seen in this thread is to buy multiple drives, and sacrifice the capacity of one of those drives to maintain single parity via a raidz1 configuration with zfs. (raidz2 or raidz3 are likely better, as you can guard against full drive failures as well, but you'd need to increase the number of drives' capacity that you're using for parity.) zfs in these filesystem-specific parity-raid implementa…
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.
Re: Unpowered SSDs slowly lose data
#124So on the off-chance that there's a firmware engineer in here, how does this actually work? Like does a SSD do some sort of refresh on power-on, or every N hours, or you have to access the specific block, or...? What if you interrupt the process, eg, having a NVMe in an external case that you just plug once a month for a few minutes to just use it as a huge flash drive, is that a problem? What about the unused space,…
Keep in mind that when flash memory is read, you don't get back 0 or 1. You get back (roughly) a floating point value -- so you might get back 0.1, or 0.8. There's extensive code in SSD controllers to reassemble/error correct/compensate for that, and LDPC-ish encoding schemes.
Modern controllers have a good idea how healthy the flash is. They will move data around to compensate for weakness. They're doing far more to detect and correct errors than a file system ever will, at least at the single-device level.
It's hard to get away from the basic question, though -- when is the data going to go "poof!" and disappear?
That is when your restore system will be tested.
Re: Unpowered SSDs slowly lose data
#125Earlier quoted context omitted.
Endurance going down is hardly a surprise given that the feature size has gone down too. The same goes for logic and DRAM memory. I suspect that 2035 years time, hardware from 2010 will work, while that from 2020 will be less reliable.
Completely anecdotal, and mostly unrelated, but my NES from 1990 is still going strong. Two PS3’s that I have owned simply broke. CRTs from 1994 and 2002 still going strong. LCD tvs from 2012 and 2022 just went kaput for no reason. Old hardware rocks.
For what it's worth my LCD monitor from 2010 is doing well. I think the power supplied died at one point but I already had a laptop supply to replace it with.
Re: Unpowered SSDs slowly lose data
#126Re: Unpowered SSDs slowly lose data
#127So on the off-chance that there's a firmware engineer in here, how does this actually work? Like does a SSD do some sort of refresh on power-on, or every N hours, or you have to access the specific block, or...? What if you interrupt the process, eg, having a NVMe in an external case that you just plug once a month for a few minutes to just use it as a huge flash drive, is that a problem? What about the unused space,…
SSD firmware engineer here. I work on enterprise stuff, so ymmv on consumer grade internals. Generally, the data refresh will all happen in the background when the system is powered (depending on the power state). Performance is probably throttled during those operations, so you just see a slightly slower copy while this is happening behind the scenes. The unused space decaying is probably not an issue, since the int…
> maybe do an fsck every month or something
Isn't that what periodic "scrub" operations are on modern fs like ZFS/BTRFS/BCacheFS?
> the data refresh will all happen in the background when the system is powered
This confused me. If it happens in the background, what's the manual fsck supposed to be for?
Re: Unpowered SSDs slowly lose data
#128Earlier quoted context omitted.
no, the firmware does any maintenance. good firmware should do gradual scrub whenever it's idle. unfortunately, there's no real way to know whether the firmware is good, or doing anything. I wonder if there's some easy way to measure power consumed by a device - to detect whether it's doing housekeeping.
Honestly this is one of my favorite things about ZFS. I know that a disk scan is performed every week/month (whatever schedule). And I also know that it has verified the contents of each block. It is very reassuring in that way.
You've validated that the scrub is actually running, right? I know that the lack of a default schedule for ZFS scrubs caused Linus Media Group to lose a bunch of archived videos to bitrot.
Re: Unpowered SSDs slowly lose data
#129How 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…
I'm seeing threads where even for HDDs people are recommending you mount them yearly to do a full check of the data and to ensure that everything keeps moving freely.
Re: Unpowered SSDs slowly lose data
#130Earlier quoted context omitted.
Who do you pay for this? (To rephrase : which cloud storage vendors do you use?) interested in the $2/month price point :)
I assume "couple of" was figurative, to indicate the cost is substantially less than managing your own bank of SSDs and ensuring it is periodically powered etc. [Edit: LOL, I see someone else posted literally the same example within the same minute. Funny coincidences.] That said, they could also be storing relatively small amounts. For example, I back up to Backblaze B2, advertised at $6/TB/month, so ~300 MB at rest…
> managing your own bank of SSDs
If I have enough data to need multiple SSDs (more than 8TB) then the cloud cost is not going to be substantially less. B2 is going to be above $500 a year.
I can manage to plug a backup SSD into a phone charger a couple times a year, or leave it plugged into one when it's not in my computer being updated. Even if I rate that handful of minutes of labor per year at a gratuitous $100, I'm still saving money well before the 18 month mark.