Not enough that I’d trust it with anything I cared about. Drives have many mechanical failure modes, the higher density ones are more exposed to media degradation, and you have different environmental concerns – e.g. flash will survive water better.
The best answer is multiple copies, preferably on different media: hedge your bets and use both, and verify it periodically so you’d know before your “working” drive throws a ton of errors when you actually try to read the data.
Well, the only thing I trust is my RAIDed ZFS with weekly scrubbing. However, that's not a backup solution. Spinning rust doesn't degrade materially over time when powered off but Flash certainly does.
> Spinning rust doesn't degrade materially over time when powered off but Flash certainly does.
Magnetic media does degrade, moving parts freeze or fail in other ways, and the circuitry can also fail. It’s often possible recover that at some cost but it’s much more expensive than n > 1 copies.
Yes, true, but for a hard disk at _rest_ (in a controlled environment) I posit it's failure distribution over time is dramatically favorable to Flash (especially TLC and QLC). I feel pretty comfortable keeping a ZFS drive pair (= mirrored) on the shelf for a decode or two whereas I'd abandon all hope for a modern SSD in the same conditions.
