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Re: [linux-lvm] LVM & snapshots



On Tue, 20 Feb 2007, Lars Ellenberg wrote:

lvm works fine for me :-)
but it won't work with 30 snapshots on one origin. not useful, anyways.
it would work ok with two to three snapshots.

I wondered if that was the case - performance?

but, just in case you want to stay with what you know,
while optimizing it: to cut the time used for your cp -al:
skip it. use the "--link-dest" option to rsync (I'm not sure which
version of rsync you need, mine is 2.6.6).

My platforms are Debian sarge - rsync is 2.6.4, but they support the --link-dest option (which would appear to be a new one for me!)

so I would do a lvm snapshot on the source, then
rsync $other_rsopts_like_include_exclude_whatever \
 -POazv '--log-format=%i %9l %n%L' \
 --link-dest /previous/backup /snapshot/mountpoint backupserver:/target
(or, if you prefer to pull, pull...)
and after that throw away the snapshot on the source machine again.

so not "snapshots as backups" on the backup server,
but as a means to get a consistent fs view on the source
for the duration of the rsync.

Right. Thanks - I'll have a look into this. I actually have 2 of these backup boxes, one on-site with the tape monster and one off-site, so this may be just what's needed for the one with the tape unit.

Cheers,

Gordon


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