this post was submitted on 26 Mar 2024
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Back when I was even less experienced in self-hosting I setup my media/backup server using a RAIDZ1 array and 3 x 8TB disks. It's been running well for a while and I haven't had any problems and no disk errors.

But today I read a post about 'pool design rules' stating that RAIDZ1 configurations should not have drives over 1TB because the chances of errors occurring during re-silvering are high. I wish I had known this sooner.

What can I do about this? I send ZFS snapshots to 2 single large (18TB) hardrives for cold backups, so I have the capacity to do a migration to a new pool layout. But which layout? The same article I referenced above says to not use RAIDZ2 or RAIDZ3 with any less than 6 drives...I don't want to buy 3 more drives. Do I buy an additional 8TB drive (for a total of 4 x 8TB) and stripe across two sets of mirrors? Does that make any sense?

Thank you!

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[–] [email protected] 0 points 7 months ago

Bit error rates have barely improved since then. So the probability of an error whenr reading a substantial fraction of a disk is now higher than it was in 2013.

But as others have pointed out. RAID is not, and never was, a substitute for a backup. Its purpose is to increase availability. And if that is critical to your enterprise, these things need to be taken into account, and it may turn out that raidz1 with 8 TB disks is fine for your application, or it may not. For private use, I wouldn't fret. but make frequent backups.

This article was not about total disk failure, but about the much more insidious undetected bit error.