[linux-lvm] LVM & snapshots

Gordon Henderson gordon at drogon.net
Tue Feb 20 15:05:06 UTC 2007

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.



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