[illumos-Developer] ZFS spare disk usage issue

[Garrett D'Amore]

On Fri, 2011-03-04 at 18:03 +0100, Roy Sigurd Karlsbakk wrote:
> So should I post a bug, or is there one there already?
> 
> Btw, I can't reach http://bugs.illumos.org/ - it times out

Try again in a few minutes... the server just got rebooted.

	- Garrett
> 
> roy
> 
> ----- Original Message -----
> > We've talked about this, and I will be putting together a fix for this
> > incorrect state handling. :-)
> > 
> > - Garrett
> > 
> > On Fri, 2011-03-04 at 11:50 -0500, Eric Schrock wrote:
> > > This looks like a pretty simple bug. The issue is that the state of
> > > the SPARE vdev is being reported as REMOVED instead of DEGRADED. If
> > > it were the latter (as it should be), then everything would work
> > > just
> > > fine. Please file a bug at bugs.illumos.org.
> > >
> > >
> > > On a side note, this continues to expose the overly simplistic vdev
> > > state model used by ZFS (one which I can take a bulk of the
> > > responsibility for). Back before the days of ditto blocks and
> > > SPA3.0,
> > > it was sufficient to model state as a fairly binary proposition. But
> > > this now has ramifications that don't necessarily make sense. For
> > > example, one may be able open a pool even if a toplevel vdev is
> > > faulted. And even when a spare has finished resilvering, it's left
> > > in
> > > the DEGRADED state, which has implications for allocation policies
> > > (though I remember discussions around changing this). But the pool
> > > state is derived directly from the toplevel vdev state, so if you
> > > switch spares to be ONLINE, then 'zpool status' would think your
> > > pool
> > > is perfectly healthy. In this case it's true from a data protection
> > > standpoint, but not necessarily from a "all is well in the world"
> > > standpoint, as you are down one spare, and that spare may not have
> > > the
> > > same RAS properties as other devices in your RAID-Z stripe (it may
> > > put
> > > 3 disks on the same controller in one stripe, for example).
> > >
> > >
> > > - Eric
> > >
> > > On Fri, Mar 4, 2011 at 7:06 AM, Roy Sigurd Karlsbakk
> > > <roy at karlsbakk.net> wrote:
> > >         Hi all
> > >
> > >         I just did a small test on RAIDz2 to check whether my
> > >         suspicion was right about ZFS not treating spares as
> > >         replicas/copies of drives, and I think I've found it true.
> > >         The
> > >         short story: If two spares replaces two drives in raidz2,
> > >         losing a third drive, even with the spares active, makes the
> > >         pool unavailable. See full report on
> > >
> > >         ODT: http://karlsbakk.net/ZFS/ZFS%20Spare%20disk%20usage.odt
> > >         PDF: http://karlsbakk.net/ZFS/ZFS%20Spare%20disk%20usage.pdf
> > >
> > >         Vennlige hilsener / Best regards
> > >
> > >         roy
> > >         --
> > >         Roy Sigurd Karlsbakk
> > >         (+47) 97542685
> > >         roy at karlsbakk.net
> > >         http://blogg.karlsbakk.net/
> > >         --
> > >         I all pedagogikk er det essensielt at pensum presenteres
> > >         intelligibelt. Det er et elementært imperativ for alle
> > >         pedagoger å unngå eksessiv anvendelse av idiomer med fremmed
> > >         opprinnelse. I de fleste tilfeller eksisterer adekvate og
> > >         relevante synonymer på norsk.
> > >
> > >         _______________________________________________
> > >         Developer mailing list
> > >         Developer at lists.illumos.org
> > >         http://lists.illumos.org/m/listinfo/developer
> > >
> > >
> > >
> > > --
> > > Eric Schrock
> > > Delphix
> > >
> > >
> > > 275 Middlefield Road, Suite 50
> > > Menlo Park, CA 94025
> > > http://www.delphix.com
> > >
> > >
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>