> Physical drives fail due to physical reasons, but SSDs fail for logical reasons.
HDD's also have a long and distinguished history of nasty firmware bugs, and this is only going to get worse as things like drive-managed SMR and hybrid flash caches get more common and their internal complexity ramps up.
Both also fail due to electrical reasons. Chips fail due to manufacturing defects, solder degrades, capacitors dry out, etc.
And I'll reiterate the uncorrected bit error rate. Transient errors are more common with SSDs, and are unlikely to happen identically with multiple units.
> If you have a mirror, and you have two identical SSDs, and you produce such a condition ... then no more mirror. They both die identically
I have a pair of mirrored SanDisk Extreme Pro's in my main server. Both suffered from a firmware bug that caused data corruption. ZFS was able to repair all damage, because they didn't fail identically.
Also thanks to the mirror I was able to upgrade the firmware without taking the server down.
Mixing different SSDs might be a good idea, but you can make much the same arguments for doing the same with HDD's, and like with HDD's it's still better than nothing to have redundancy with "identical" drives.
HDD's also have a long and distinguished history of nasty firmware bugs, and this is only going to get worse as things like drive-managed SMR and hybrid flash caches get more common and their internal complexity ramps up.
Both also fail due to electrical reasons. Chips fail due to manufacturing defects, solder degrades, capacitors dry out, etc.
And I'll reiterate the uncorrected bit error rate. Transient errors are more common with SSDs, and are unlikely to happen identically with multiple units.
> If you have a mirror, and you have two identical SSDs, and you produce such a condition ... then no more mirror. They both die identically
I have a pair of mirrored SanDisk Extreme Pro's in my main server. Both suffered from a firmware bug that caused data corruption. ZFS was able to repair all damage, because they didn't fail identically.
Also thanks to the mirror I was able to upgrade the firmware without taking the server down.
Mixing different SSDs might be a good idea, but you can make much the same arguments for doing the same with HDD's, and like with HDD's it's still better than nothing to have redundancy with "identical" drives.