HAST + ZFS self healing? Hot spares?

[Pawel Jakub Dawidek]

On Wed, May 18, 2011 at 10:37:50AM +0200, Per von Zweigbergk wrote:
[...]
> This would mean that you'd be running a stack looking like:
> - ZFS on top of:
> - One HAST resource on top of:
> - Two ZVOLs, each on top of:
> - ZFS on top of:
> - Local storage (mirrored by zfs)

Having recursive ZFS pools is bad idea and most likely it was cause
deadocks. You also pay all the costs with checksumming, ARC cache, etc.
twice. Very bad idea.

> >Some reported they used HAST for the SLOG as well. I do not know
> >if using HAST for the L2ARC makes any sense. On failure you will
> >import the pool on the slave node and this will wipe the L2ARC
> >anyway.
> Yes, running HAST on L2ARC doesn't make much sense, I'd have to run
> HAST on the ZIL though if I opted for Variant 1 (which I don't think
> I will).

Using HAST for L2ARC devices might make no sense, but they are part of
the pool. So if you import the pool on another machine L2ARC device will
be failed. You may experiment with importing the pool, removing current
L2ARC devices and attaching machine-local L2ARC devices. This way you
avoid HAST for L2ARC, but not sure how reliable can that be.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://yomoli.com
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