[Linux-cluster] How backup domU partition from dom0?

[Fajar A. Nugraha]

On Fri, Sep 4, 2009 at 7:08 PM, Miguel Sanchez<ntadmin at fi.upm.es> wrote:
> Hi. I have two hosts forming a cluster for run xen vm's. Each vm has a disk
> which is corresponding to a clvm logic volume within dom0.
> I pretended to backup the lv's from dom0 doing a 'kpart -a' and a readonly
> mount (with the vm running). Probably it is not very correct (but the
> alternative snapshot was not possible with clvm).

Did you know that if you mount an ext3 partition READ ONLY you could
actually do a WRITE to that partition to replay the journal, and so
cause possible data corruption?

> Most of times, the operation is ok, and the backup finishes with problems,
> but in other cases 'mount -r /dev/mapper/device /path' does not return and
> it stays consuming time indefinitely. I cannot kill the process y have to
> fence the node.
>
> How could I make the domU backups within dom0 without these problems?

You can't. Not without clvm snapshot.
What you could probably do :
- do backup from within domU
- do backup from the SAN, if it supports snapshot.

-- 
Fajar