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Unpowered SSDs slowly lose data
101–110 of 341 posts
Re: Unpowered SSDs slowly lose data
#102So, product idea: A powered "cold storage box" for M.2 SSDs. 2 to 8 M.2 slots. Periodically, an internal computer connects one of the slots, reads every byte, waits for some period of time, then powers off. Maybe shows a little green light next to each drive when the last read was successful. Could be battery-powered.
Re: Unpowered SSDs slowly lose data
#103So, product idea: A powered "cold storage box" for M.2 SSDs. 2 to 8 M.2 slots. Periodically, an internal computer connects one of the slots, reads every byte, waits for some period of time, then powers off. Maybe shows a little green light next to each drive when the last read was successful. Could be battery-powered.
> Could be battery-powered.
How often does it need to run? If it could be solar powered you could probably avoid a whole bunch of complexity per unit longevity.
Re: Unpowered SSDs slowly lose data
#104What is the best way to store data for a long time then?
Depending on your time requirements, carving it into a stone tablet is generally a good choice
Re: Unpowered SSDs slowly lose data
#105One key point about retention which is not often mentioned, and indeed neither does this article, is that retention is inversely proportional to program/erase cycles and decreases exponentially with increasing temperature. Hence why retention specs are usually X amount of time after Y cycles at Z temperature. Even a QLC SSD that has only been written to once, and kept in a freezer at -40, may hold data for several de…
I also seem to remember reading retention is proportional to temperature at time of write. Ie, best case scenario = write data when drive is hot, and store in freezer. Would be happy if someone can confirm or deny this.
That's probably this: https://www.sciencedirect.com/science/article/abs/pii/S00262...
Re: Unpowered SSDs slowly lose data
#106Earlier quoted context omitted.
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…
>Generally, the data refresh will all happen in the background when the system is powered (depending on the power state). How does the SSD know when to run the refresh job? AFAIK SSDs don't have an internal clock so it can't tell how long it's been powered off. Moreover does doing a read generate some sort of telemetry to the controller indicating how strong/weak the signal is, thereby informing whether it should ref…
Pretty much, but it depends a lot on the vendor and how much you spent on the drive. A lot of the assumptions about enterprise SSDs is that they’re powered pretty much all the time, but are left in a low power state when not in use. So, data can still be refreshed on a timer, as long as it happens within the power budget.
There are several layers of data integrity that are increasingly expensive to run. Once the drive tries to read something that requires recovery, it marks that block as requiring a refresh and rewrites it in the background.
Re: Unpowered SSDs slowly lose data
#107What about powered SSDs that contain files that are rarely read? My desktop computer is generally powered except when there is a power failure, but among the million+ files on its SSD there are certainly some that I do not read or write for years. Does the SSD controller automatically look for used blocks that need to have their charge refreshed and do so, or do I need to periodically do something like "find / -type…
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.
Re: Unpowered SSDs slowly lose data
#108One key point about retention which is not often mentioned, and indeed neither does this article, is that retention is inversely proportional to program/erase cycles and decreases exponentially with increasing temperature. Hence why retention specs are usually X amount of time after Y cycles at Z temperature. Even a QLC SSD that has only been written to once, and kept in a freezer at -40, may hold data for several de…
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.
Re: Unpowered SSDs slowly lose data
#109So, product idea: A powered "cold storage box" for M.2 SSDs. 2 to 8 M.2 slots. Periodically, an internal computer connects one of the slots, reads every byte, waits for some period of time, then powers off. Maybe shows a little green light next to each drive when the last read was successful. Could be battery-powered.
How much are you saving vs an always-on ARM board with M.2 slots? Is it worth the pennies?
Re: Unpowered SSDs slowly lose data
#110Earlier quoted context omitted.
Huh. I wonder if this is why I'd sometimes get random corruption on my laptop's SSD. I'd reboot after a while and fsck would find issues in random files I haven't touched in a long time.
Unless your setup is a very odd Linux box, fsck will never check the consistency of file contents.
A ZFS scrub (default scheduled monthly) will do it.