zfs discuss - May 2007 - Re: A quick ZFS question: RAID-Z Disk Replacement + Growth ?

Hi All,

My mate Chris posed me the following; rather than flail about with
engineering friends trying to get a "definitive-de-jour" answer, 
I thought instead to introduce him to the relevant opensolaris forum
in the hope of broadening the latter''s appeal.

So: RAID-Z hot swap to larger disks and thereby upgrade?  

Doable, not, or unwise?

I suspect the proper thing to do would be to build the six new large
disks into a new RAID-Z vdev, add it as a mirror of the older,
smaller-disk RAID-Z vdev, rezilver to zynchronize them, and then break
the mirror.

But I''d like a second opinion?

	- alec


 >Hiya Alec,
 >
 >Mark Baily here at VPAC asked me a ZFS question which I can''t
answer
 >(except by guessing) and I said I''d ask you in case you had a
quick
 >answer as you''ve played with it a bit more.
 >
 >Mark wrote:
 >
 >> Can the pool''s size be increased by replacing [6 old 320Gb
disks]
 >> with a new set of 6 HD''s say 640GB each, changing one disk at
a
 >> time and waiting for data to be resilvered before replacing the
 >> next disk, then when all 6 disks are resilvered the size will
 >> automatically be doubled?
 >
 >My guess is that the answer would be yes, that should work, but that
 >is just a guess!  Is this something you''ve played with ?
 >
 >cheers!
 >Chris

-- 
Alec Muffett
http://www.google.com/search?q=alec+muffett

I did this on Solaris 10u3.  4 120GB -> 4 500GB drives.  Replace, resilver;
repeat until all all drives replaced.

On 5/14/07, Alec Muffett <Alec.Muffett at sun.com>
wrote:
>
>
>
> Hi All,
>
> My mate Chris posed me the following; rather than flail about with
> engineering friends trying to get a "definitive-de-jour" answer,
> I thought instead to introduce him to the relevant opensolaris forum
> in the hope of broadening the latter''s appeal.
>
> So: RAID-Z hot swap to larger disks and thereby upgrade?
>
> Doable, not, or unwise?
>
> I suspect the proper thing to do would be to build the six new large
> disks into a new RAID-Z vdev, add it as a mirror of the older,
> smaller-disk RAID-Z vdev, rezilver to zynchronize them, and then break
> the mirror.
>
> But I''d like a second opinion?
>
>         - alec
>
>
> >Hiya Alec,
> >
> >Mark Baily here at VPAC asked me a ZFS question which I can''t
answer
> >(except by guessing) and I said I''d ask you in case you had a
quick
> >answer as you''ve played with it a bit more.
> >
> >Mark wrote:
> >
> >> Can the pool''s size be increased by replacing [6 old
320Gb disks]
> >> with a new set of 6 HD''s say 640GB each, changing one
disk at a
> >> time and waiting for data to be resilvered before replacing the
> >> next disk, then when all 6 disks are resilvered the size will
> >> automatically be doubled?
> >
> >My guess is that the answer would be yes, that should work, but that
> >is just a guess!  Is this something you''ve played with ?
> >
> >cheers!
> >Chris
>
> --
> Alec Muffett
> http://www.google.com/search?q=alec+muffett
>
>
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
>
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zfs-discuss-bounces at opensolaris.org wrote on 05/14/2007 02:10:28 PM:
> I did this on Solaris 10u3.  4 120GB -> 4 500GB drives.  Replace,
> resilver; repeat until all all drives replaced.
Just beware of the long resilver times -- on a 500gb x 6 raidz2 group at
70% used space a resilver takes 7+days where snaps do not work and the
disks are pegged (system almost unusable).  If that is OK by you then a
resilver may be the best method.  For it to work for me I would need the
rebuild times much quicker or be able to throttle them down so the system
is usable.  Either way no snapshots while resilvering means ZFS can''t
be
used on our bigger workloads anyways.

-Wade

On Mon, 14 May 2007, Alec Muffett wrote:
> I suspect the proper thing to do would be to build the six new large
> disks into a new RAID-Z vdev, add it as a mirror of the older,
> smaller-disk RAID-Z vdev, rezilver to zynchronize them, and then break
> the mirror.
The ''zpool replace'' command is a more direct way to do this,
rather than
messing about with adding and removing mirrors.


Regards,
markm