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Date:      Sat, 22 Sep 2012 22:59:56 -0600
From:      "Justin T. Gibbs" <gibbs@scsiguy.com>
To:        Andriy Gapon <avg@freebsd.org>
Cc:        freebsd-fs@freebsd.org
Subject:   Re: zfs: allow to mount root from a pool not in zpool.cache
Message-ID:  <DA42C8E9-BFFF-4C5A-9E14-1D50EAEFA669@scsiguy.com>
In-Reply-To: <505DE715.8020806@FreeBSD.org>
References:  <505DE715.8020806@FreeBSD.org>

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On Sep 22, 2012, at 10:28 AM, Andriy Gapon <avg@freebsd.org> wrote:

>=20
> Currently FreeBSD ZFS kernel code doesn't allow to mount root =
filesystem on a
> pool that is not listed in zpool.cache as only pools from the cache =
are known to
> ZFS at that time.

I've for some time been of the opinion that FreeBSD should only use
the cache file for ZFS pools created from non-GEOM objects (i.e.
files).  GEOM tasting should be used to make the kernel aware of
all pools whether they be imported on the system, partial, or
foreign.  Even for pools created by files, the user land utilities
should do nothing more than ask the kernel to "taste them".  This
would remove code duplicated in user land for this task (code that
must be re-executed in kernel space for validation reasons anyway)
and also help solve problems we've encountered at Spectra with races
in fault event processing, spare management, and device arrival and
departures.

So I'm excited by your work in this area and would encourage you
to "think larger" than just trying to integrate root pool discovery
with GEOM.  Spectra may even be able to help in this work sometime
in the near future.

--
Justin



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