Re: [Xen-users] iSCSI Volumes and Xen

["Matthew Law" <matt@xxxxxxxxxxxxxxxxxx>]

On Thu, January 14, 2010 4:55 pm, Fajar A. Nugraha wrote:
> I'd step back a bit and look at what kind of application are you
> trying to back up.
> If they're applications that can survive unclean shutdown or server
> power outage (like most modern ACID database with journaling), then
> most likely a simple zfs/lvm snapshot is enough. "xm suspend" or "xm
> save" is similar to having suspend/hibernate on the server, not needed
> if you already have zfs/lvm snapshot.
>
> In some cases, taking zfs/lvm snapshot can actually be BETTER compared
> to having backup software on domU.
> For example: you run MySQL on domU with innodb storage engine, and
> your backup software can only backup filesystem. In this scenario, if
> you backup the innodb files directly from domU, and domU doesn't use
> LVM, then most likely the backup will be useless as the files will not
> be  from the same time (i.e. some could be changed when the backup
> process is running). However, if you do this from dom0 side with
> zfs/lvm snapshot, the files will be consistent enough that MySQL
> should be able to replay the journal and function normally afterwards.

I don't have any idea what my users will be running on them.  I was hoping
that taking a daily snapshot of the 'suspended state' of the domU and
archiving it off the dom0 would be an acceptable 'last resort'.  Even if
the data is inconsistent, it would be nice to be able to get back to a
running, stable domU OS if I have to recover from something catastrophic.

If they need quality incremental backups they need to do those themselves
with the backup scheme for their apps and data.  I would help with storing
those off the domU, but I can't realistically backup the entire thing with
great certainty, it would seem.

Hope this makes sense and doesn't sound reckless because that isn't the
intention.

Thanks,

Matt


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