Re: [linux-lvm] Snapshot rollback

[Mike Snitzer <snitzer@redhat.com>]

On Wed, Feb 24 2010 at  5:46pm -0500,
Eric Brunson <brunson@brunson.com> wrote:

> On 09/23/2009 03:40 PM, Alasdair G Kergon wrote:
> >On Wed, Sep 23, 2009 at 03:04:22PM -0600, Eric Brunson wrote:
> >>I remember seeing somewhere discussion of adding the ability to roll
> >>back to a snapshot.  I think of how cool this would be about ever six
> >>months, usually coinciding with an impending Fedora release.  ;-)
> >The developers are just starting to submit their patch sequence to the
> >development mailing lists (dm-devel and lvm-devel) for review.  So
> >that's targetting linux-next in the next few weeks ready for the 2.6.33
> >kernel.
> >
> 
> From the newly released 2.6.33 kernel changelog, does this mean what
> I think it means?
> 
>    commit 53365383c4667aba55385cd1858582c19a7a8a36
>    Merge: 51b736b d2fdb77
>    Author: Linus Torvalds<torvalds@linux-foundation.org>
>    Date:   Tue Dec 15 09:12:01 2009 -0800
> 
>         Merge git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm
> 
>         * git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-2.6-dm: (80 commits)
>           dm snapshot: use merge origin if snapshot invalid
>           dm snapshot: report merge failure in status
>           dm snapshot: merge consecutive chunks together
>           dm snapshot: trigger exceptions in remaining snapshots during merge
>           dm snapshot: delay merging a chunk until writes to it complete
>           dm snapshot: queue writes to chunks being merged
>           dm snapshot: add merging
>           dm snapshot: permit only one merge at once
>           dm snapshot: support barriers in snapshot merge target
>           dm snapshot: avoid allocating exceptions in merge
>           dm snapshot: rework writing to origin
>           dm snapshot: add merge target
>           dm exception store: add merge specific methods
>           dm snapshot: create function for chunk_is_tracked wait
>           dm snapshot: make bio optional in __origin_write
>           ...
> 
> 
> If it does, then I'm very excited.  :-)

Ha, yes the 2.6.33 kernel includes DM's new snapshot-merge target.

LVM2 >= 2.02.59 provides userspace support for snapshot-merge (via
lvconvert --merge).  Though 2.02.61 adds the ability to tag N snapshots
with a common tag and then merge them all back to their respective
origin using: lvconvert --merge @tag

Mike