[OpenIndiana-discuss] Resilver restarting on second dead drive?

[David Brodbeck]

On Thu, Feb 9, 2012 at 1:13 PM, Roy Sigurd Karlsbakk <roy at karlsbakk.net>wrote:

> Now, I can somewhat see the argument in resilvering more drives in
> parallel to save time, if the drives fail at the same time, but how often
> do they really do that? Mostly, a drive will fail rather out of sync with
> others. This leads me to thinking it would be better to let the pool
> resilver the first device dying and then go on with the second, or perhaps
> allow for manual override somewhere.
>

In my experience it's often the resilvering process that triggers the
failure of the second drive -- and this is an issue with RAID in general,
not just with ZFS.  The reason is you're suddenly forcing a read of all the
the data on all the remaining drives, and this can uncover latent failures.
 It's also not that uncommon for a hotspare to turn out to be bad -- after
all, it's been spinning just as long as the rest of the disks.

This is, incidentally, why I don't run single-parity RAID anymore.  That
and I like to stay in bed at night. ;)

-- 
David Brodbeck
System Administrator, Linguistics
University of Washington