Got a call at 4am - RAID Gurus Please Read

Rob Seastrom rs at
Wed Dec 10 13:40:21 UTC 2014

The subject is drifting a bit but I'm going with the flow here:

Seth Mos <seth.mos at> writes:

> Raid10 is the only valid raid format these days. With the disks as big
> as they get these days it's possible for silent corruption.

How do you detect it?  A man with two watches is never sure what time it is.

Unless you have a filesystem that detects and corrects silent
corruption, you're still hosed, you just don't know it yet.  RAID10
between the disks in and of itself doesn't help.

> And with 4TB+ disks that is a real thing.  Raid 6 is ok, if you accept
> rebuilds that take a week, literally. Although the rebuild rate on our
> 11 disk raid 6 SSD array (2TB) is less then a day.

I did a rebuild on a RAIDZ2 vdev recently (made out of 4tb WD reds).
It took nowhere near a day let alone a week.  Theoretically takes 8-11
hours if the vdev is completely full, proportionately less if it's
not, and I was at about 2/3 in use.


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