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Date:      Thu, 11 Jan 2007 15:01:52 -0500
From:      Kris Kennaway <kris@obsecurity.org>
To:        Scott Oertel <freebsd@scottevil.com>
Cc:        Willem Jan Withagen <wjw@digiware.nl>, freebsd-stable@freebsd.org, Kris Kennaway <kris@obsecurity.org>
Subject:   Re: running mksnap_ffs
Message-ID:  <20070111200152.GA36123@xor.obsecurity.org>
In-Reply-To: <45A68F2E.6040205@scottevil.com>
References:  <459ABB40.7050603@digiware.nl> <20070111153651.GC31382@xor.obsecurity.org> <45A68F2E.6040205@scottevil.com>

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On Thu, Jan 11, 2007 at 11:25:34AM -0800, Scott Oertel wrote:
> Kris Kennaway wrote:
> >On Tue, Jan 02, 2007 at 09:06:24PM +0100, Willem Jan Withagen wrote:
> > =20
> >>Hi,
> >>
> >>I got the following Filesystem:
> >>Filesystem    Size    Used   Avail Capacity iused     ifree %iused=20
> >>/dev/da0a     1.3T    422G    823G    34%  565952 182833470    0%
> >>
> >>Running of a 3ware 9550, on a dual core Opteron 242 with 1Gb.
> >>The system is used as SMB/NFS server for my other systems here.
> >>
> >>I would like to make weekly snapshots, but manually running mksnap_ffs=
=20
> >>freezes access to the disk (I sort of expected that) but the process=20
> >>never terminates. So I let is sit overnight, but looking a gstat did no=
t=20
> >>reveil any activity what so ever...
> >>The disk was not released, mksnap_ffs could not be terminated.
> >>And things resulted in me rebooting the system.
> >>
> >>So:
> >> - How long should I expect making a snapshot to take:
> >>	5, 15, 30min, 1, 2 hour or even more???
> >>   =20
> >
> >Yes :) Snapshots were not designed for use in this way (they were
> >designed to support background fsck and allow faster system recovery
> >after power failure), so they don't scale as well as you might like on
> >large filesystems.
> >
> >Kris
> > =20
>=20
>=20
> If snapshots were designed to support background fsck, then why did they=
=20
> not make it more scalable? If you can't create a snapshot without the=20
> system locking up, that means fsck won't be able to either, making=20
> background fsck worthless for systems with large storage.

locking up !=3D taking a long time to complete.  You haven't
differentiated between those two situations yet.

Kris

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