[linux-lvm] restoring snapshots
David.Kinzel at encana.com
Mon Sep 20 13:15:10 UTC 2010
>I was wondering about how to restore/apply a LVM snapshot to the
>original partition. Looking at the archive, I can see it's
>advised to dump the snapshot content into a file and then dump
>that onto the original device after having removed the snapshot.
>What's wrong with:
>lvcreate -n lv -L1G vg
>mount /dev/vg/lv /x
>lvcreate -s -n lv_snap /dev/vg/lv
>mount /dev/vg/lv_snap /y
>Them to apply the snapshot:
>umount /x /y
>dd bs=4M < /dev/mapper/vg-lv_snap > /dev/mapper/vg-lv-real
>It's still not optimal as it writes the whole volume, but at
>least, I don't have to find a storage area big enough to hold an
>extra copy of the whole volume and it's faster.
>It seems to be working on a test on /dev/loop. Is there any
>circumstance (as long as there's only one snapshot of the
>volume) where it wouldn't work, or what would be the potential
>pitfalls (other than if there's a crash in the middle, you're
>Is there any plan to add the feature to efficiently
>restore/apply/commit a snapshot (that is only dump the cow data
>onto the original volume without writing the whole volume) or
>does that feature exist already and I missed it?
The newer versions do have the lvmerge feature, and it seems to work in
RHEL6 beta from what I could see.
>linux-lvm mailing list
>linux-lvm at redhat.com
>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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