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

[Martin Frost]

 > Date: Thu, 9 Feb 2012 13:50:47 -0800
 > From: David Brodbeck <brodbd at uw.edu>
 > 
 > 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. ;)

Does ZFS periodically verify hot spares?  For that matter, does it
verify the RAIDZ disks?

Martin