From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Fri, 19 Oct 2001 09:08:53 +0100
Subject: Re: [linux-lvm] SnapRestore software on NetApp
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References: <0110181646580Y.24876@in-cadcae4> <20011018174818.C849@btconnect.com> <20011018122021.G1144@turbolinux.com>
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In-Reply-To: <20011018122021.G1144@turbolinux.com>; from adilger@turbolabs.com on Thu, Oct 18, 2001 at 12:20:22PM -0600
From: Joe Thornber <thornber@btconnect.com>
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On Thu, Oct 18, 2001 at 12:20:22PM -0600, Andreas Dilger wrote:
> This may be possible to do in the short term with writable snapshots,
> but then you start getting into a very ugly situation where the "good"
> volume (i.e. the writable snapshot) depends on the snapshot, which
> depends on the original "bad" volume and you can't get rid of any of them.

I suppose the ideal solution is to allow people to choose which way
round a snapshot is taken depending on whether they thinks it's likely
they'll rollback, or commit to the snapshot.

ie.

You probably want to rollback; the snapshot lv contains new data written to 
the snapshot (as it is now).  Rollback is quick, commit (merge) is slow.

You probably want to commit to the snapshot; the snapshot lv contains
copies of the original data.  Rollback (merge) is slow, commit is quick.

- Joe