Re: Proper method of snapshotting XFS with external log using LVM2

[David Chinner <dgc@sgi.com>]

On Mon, Jul 30, 2007 at 07:32:18AM +1200, Mario Becroft wrote:
> I am using XFS and LVM2 under Linux. My XFS filesystems have an external
> log.
> 
> What is the correct method of creating an LVM2 snapshot of volumes
> containing an XFS filesystem with external log?

Not sure. I've never tried it.

> Do I need to snapshot the main filesystem volume and the log volume?

Yes.

> Should I be using xfs_freeze to ensure that the filesystem is not
> modified between when I create the filesystem snapshot and the log
> snapshot?

Yes.

> Or is there a special procedure for atomically creating both snapshots?
>
> Or should I not be using an external log? If not, won't this decrease
> performance?

If it doesn't work, then don't use an external log and yes, it will
decrease performance.

> In the past I have successfully used xfs_freeze and created separate
> snapshots of the filesystem and log volumes. However, I am not sure
> whether this is the recommended approach.

As long as both snapshots were taken with the one xfs_freeze command,
then it shouldbe ok.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group