[linux-lvm] CLVM Snapshot HOWTO?

Vu Pham vu at sivell.com
Tue Mar 24 03:34:16 UTC 2009

Paul Dugas wrote:
> I apologize if this has been covered already or is written up elsewhere
> but I can't seem to find it.  I've got a couple of AoE volumes that I'm
> using for LVM VGs.  They have GFS filesystems on LVs that are sized to
> fill 90% of the the VGs; 10% space left over for snapshots.  I have 4
> CENTOS 5.2 machines clustered and mounting the GFS filesystems.  That's
> working well.
> Having used LVM snapshots in non-cluster environments before, I figured
> I'd just use the same logic for backing up the volumes; lvcreate -s,
> mount, backup, umount, lvremove.  This quickly fell apart and I started
> to think about it more.  I ended up wondering how snapshots of the
> volume could ever really work without coordinating with the other
> nodes.  
> My question is this.  Should I be able to use snapshots on clustered
> volumes like this?  If not, are there plans to support it later?  If so,
> can someone point me to a working example?

I think you have to freeze the GFS volume before you create a snapshot, 
then you unfreeze it. man gfs_tool


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