[linux-lvm] efficiently copying snapshot data.

Ray Morris support at bettercgi.com
Sat Jul 10 01:14:11 UTC 2010

> > rsync/

> That doesn't do what he wants.  He wants to copy only
> the COW blocks.

   The COW blocks being those that are different between the
master and the snapshot, correct?  Have I been doing it wrong
all of these years, because I was under the distinct impression
that rsync copied only the differences.

    Perhaps the confusion is here is whether he wants the destination
to include nothing but the changed the blocks, but that doesn't
require any new LVM programming.  If you want the destination to be
a snapshot, only the differences, just take a snapshot on the
new machine and rsync from the old snapshot to the new snapshot.
A very few blocks might get duplicated because of file level versus
block level, but in practice that hasn't seemed to be significant.
At least, not for our 160 or so VMs.
Ray Morris
support at bettercgi.com

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