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Slight digression here but "RAID 1 SSD" might not be a good idea, especially if you bought two SSDs at the same time. They are probably from the same lot. My experience with 3,000 SSDs in use is that they seem to fail with a combination of age and rewrites. So I would be concerned that two equivalently aged SSDs with an equivalent set of rewrites (as RAID 1 does) would be quite likely to fail at the same time, or more precisely, when one failed you probably have a statistically harder time recovering the mirror from the other.

That is just statistics of course, but one of the things I tried to do in the Blekko infra-structure was to mix the ages of the SSDs to mitigate this risk.




This is good advice even for spinning disks. I once met an unlucky RAID-5 array of three identical disks from the same brand, model, batch and with close serial numbers. When one of them failed, I immediately ordered 3 replacements.

They didn't arrive on time.

Good thing I had backups.


I've heard there's strong correlation in failures by lot number. Can you confirm this?

What's the practical way to avoid this? Staggering your SSD purchases?




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