Jeremy Nicoll writes:
On Wed, 11 Jan 2023, at 14:58, Tom Browder wrote: > I plan to install a 4-bay, hot swappable SSD dock to replace the existing > DVD in my only 5.5" externally accesible bay. To fill it, I will get up to > four 2.5 inch SSDs of 1 Tb: MX500 by Crucial. My plan is to use the SSDs > for backup, but not in a RAID configuration. I can't advise on choice of dock etc, but I'm interested in the side issue of how long an unpowered SSD can be assumed still to be holding the data written to it. Does one need (just) to mount the drive once in a while? (How often?) Or does one need (say) to read every file on the drive once, so that the SSD controller can assess whether any data needs to be moved? Or does one need to read every byte, allocated or not?
AFAIK one needs to _power_ the device every once in a while and keep power connected for some time. Then, the controller can dos all the necessary actions in the background.
A long time ago, companies claimed data retention for 10 years (that was: for SLC drives!). The latest figure that I am aware of was 1 year (maybe for TLC?). I think the trend is that manymanufacturers do not publish any data retention times for consumer drives (newly QLC) anymore. One can only guess or measurea.
For backup purposes, I believe the advantage of SSDs over HDDs is mostly that they are shock resistant. If this is of no concern, I'd prefer to backup to HDDs instead of SSDs because of the data retention issue and in general a higher chance of rescuing data from the drive in event of failure.
Here is an article from 2021 that shows some typical numbersas I remembered them. I do not know anything about this specific source's credibility, though:
https://www.virtium.com/knowledge-base/ssd-data-retention/ This entry seems to be rather pessimistic: https://www.ibm.com/support/pages/potential-ssd-data-loss-after-extended-shutdownIBM says that for enterprise drives (typically higher quality than consumer- grade drives) only three months of data retention are guaranteed at 40°C. And: This article is from 2021, too...
YMMV Linux-Fan öö
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