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So I have an Samsung 240gb 840 EVO that I upgraded to an 500gb 860 EVO, I want to keep the old one as a backup (So i can swap it back in if the new one fails (it is the Operating system drive)). I am a bit late to this as I actually replaced it about a year and half ago (so the old SSD has now been sat on the shelf for about 1 and a bit years) and have just bought an external usb enclosure for it. Currently doing an error check on it (the 840 evo). (Ok it said it would take 3 hours , it lied it took about 10-15mins) and came back saying no errors. Which is nice but surprised me !

I have heard that leaving it on the shelf too long will corrupt the data, so I figure I can stop this by plugging it in every so often.

So the question is if I plug it in say every month or 2 to keep it refreshed, how long do I need to leave it on for ? Is it like 2 seconds or a couple of hours ? Is there something built into the SSD controller itself to keep the data topped up, or is it done by the operating system (win 10)? And if it is windows itself topping it up is being externally mounted on the USB ok, or does it need to be plugged directly into the SATA ?

Also what is the top up mechanism, is it there is some kind of capacitor or battery in the SSD that needs topping or does it go around and re write all the data or is it that it doesn't top it up and leaving it unpowered is a cumulative thing that eventually destroys the data even if you keep plugging it in every so often?

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    extremetech.com/computing/…
    – Moab
    Commented Jul 14, 2020 at 12:25
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    SSD's should not be used for critical data storage.
    – Moab
    Commented Jul 14, 2020 at 12:27
  • As ssds are generally a lot more reliable than hdds they seem as good as anything to rely on for a backup, if you can somehow maintain the data on them, hence the question. In regards to the article you quoted I think my ssd was probably mostly sat at 25-35 c degrees with a max of maybe 45 when in use and prob mostly about 15 -20 degrees when on sat on a shelf. Í bought the 860 in nov 18 (black friday) but it took me 3- 6 months to get around to fitting it !
    – MajorTom
    Commented Jul 14, 2020 at 12:44

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Normal (retail) SSD will take about 2 years at 25 degrees celsius on the shelf before they loose data. Note however, that this is a statistical average, not a guarantee. Hotter means earlier.

If you want to get into the nitty-gritty details of the why: it is because electrons migrate through the semiconductors. And a higher temperature makes the semiconductor more conductor. (I know, very cryptic, but it requires quite a long explanation)

I have not found any information about how long you need to plug it in, or whether you actually need to read on the drive. The problem is probably that an experiment takes too long to say anything valuable about this.

As a comparaison some very rough figures:

  • SSD: up to 2 years
  • spinning rust: 9-20 years
  • Tape: around 30 years
  • cd/dvd: up to 25 years
  • Hieroglyphs: over 2000 years :-)

Anyway: for real long-term storage, you need to make frequent copies. A librarian once told me that archiving is copying. And in IT, doubly so. For example: a drive may contain the data, but I am no longer able to read my old ultra-wide SCSI drives. Or even: how do I read my Vistasource Applixware or Wordperfect 5.1 files?

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  • Does this migration occur regardless of if they are plugged in or not ? And if so why is having it plugged in for 3 years better than having it unplugged for 3 years in terms of data retention ?Oh I did find this about the 840 evo specifically, but it still doesnt mention how long it needs leaving on for link
    – MajorTom
    Commented Jul 14, 2020 at 15:21
  • That is interesting. In a very gross simplification, it suggests that you need to rewrite your data once every time. So, plugging in and reading is not enough.On the other hand: it does not give a target time for how long you should plug it in ("It's unclear how long the EVO will take to optimize itself after extended downtime.")
    – Ljm Dullaart
    Commented Jul 14, 2020 at 16:04
  • Keeping it plugged in allows the drive's firmware to rewrite from time to time. That is a reason why keeping it plugged-in is better.
    – Ljm Dullaart
    Commented Jul 14, 2020 at 16:05
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    Ljm I think you are probably correct. Hmm so maybe the answer isnt seconds or hours, but rather days, weeks or months for it to refresh it (re write it) in the background ! It would be nice to know which it is ! It would also be nice if there was some official way to keep the data good.
    – MajorTom
    Commented Jul 14, 2020 at 21:33
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    Making frequent copies is a nice theory! 2tb of external backup is fat32. Windows wont back up the os to an external drive, other cloning stuff wont copy to a fat 32. I spent 2 hours trying to get acronis to copy from another failing hard disk to a new 2tb ssd, only for it to give me a "could not schedule this operation", at the end. Not that it could even find the drive until I had formatted it! Backing up is nice in theory but they go waaay out of their way to make it a pain in practice, just so they can sell you cloud backup! Ended up copying the stupid 1.8 million files with explorer !
    – MajorTom
    Commented Jul 14, 2020 at 21:47

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