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Re: [linux-lvm] restoring snapshots



>Hiya,
>
>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
>lvremote /dev/vg/lv_snap
>
>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
>screwed)?
>
>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.

>
>Thanks,
>Stephane
>
>_______________________________________________
>linux-lvm mailing list
>linux-lvm redhat com
>https://www.redhat.com/mailman/listinfo/linux-lvm
>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

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