[dm-devel] "create snapshots of any block device"
Bryn M. Reeves
bmr at redhat.com
Tue Jan 22 11:22:27 UTC 2013
On 01/22/2013 11:12 AM, Hauke Laging wrote:
> Isn't that at least misleading? Is it really possible to create a snapshot of
> e.g. /dev/sda5 without creating an *additional* device as snapshot origin?
It's possible but as you note you have to create the dm layers for the
snapshot. This means that if a non-dm device is in use you have to shut
its users down (unmount file systems etc.), create the snapshot and then
re-mount.
I've frequently used this in the past to snapshot large zero targets to
create sparse devices for testing (before --virtualsize was added to LVM2).
With device-mapper devices this is unnecessary since the top-level
device may be suspended while the snapshot layers are inserted.
Regards,
Bryn.
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