LVM Snapshot Merging
(Sat, 09 Aug 2008 18:02:48 +0000)
Mikulas Patocka announced new patches introducing snapshot merging for the Linux kernel's logical volume manager. He explained, "snapshot merging allows you to merge snapshot content back into the original device. The most useful use for this feature is the possibility to rollback [the] state of the whole computer after [a] failed package upgrade, [or an] administrator's error". The patches are for the 2.6.26 kernel, with device mapper 1.02.27 and LVM2.2.02.39.
Mikulas noted that there are three types of merges supported, --nameorigin, --namesnapshot, and --onactivate. The default merge method is --nameorigin, which can merge a snapshot into the origin volume, which can be mounted at any time after the merge starts. The --namesnapshot method merges into a snapshot, which can then be mounted. And the --onactive method schedules a merge to happen the next time the volume is activated, such as during a reboot. Mikulas noted, "this implementation of snapshot merging is meant to be stable, report any possible bugs to me."