Re: [Xen-users] snapshots on xen

[James Pifer <jep@xxxxxxxxxxxxxxxx>]

On Mon, 2010-04-12 at 09:20 +0300, Pasi KÃrkkÃinen wrote:
> On Sat, Apr 10, 2010 at 08:58:59AM -0400, James Pifer wrote:
> > On Sat, 2010-04-10 at 13:55 +0300, Pasi KÃrkkÃinen wrote:
> > > On Fri, Apr 09, 2010 at 08:57:16PM -0400, James Pifer wrote:
> > > > Hi all. I'm using sles11 for my xen servers. I would really like to be
> > > > able to do hot snapshots of disk AND memory, and then have these
> > > > snapshots backed up to tape or off site for disaster recovery. I'm
> > > > thinking this would be done weekly or monthly, not nightly.
> > > > 
> > > > Two questions:
> > > > 
> > > > 1) Is this even possible? 
> > > >
> > > 
> > > 1) xm save <guest> <guest>.save
> > > 2) save a copy of the guest disks
> > > 3) save a copy of the <guest>.save file
> > > 4) xm restore <guest>.save
> > >  
> > 
> > Pasi,
> > 
> > Thanks for the reply. Questions based on your response:
> > 
> > 1) Is this dependent on the file system at all? 
> > 
> 
> No, it's not.
> 
> > 2) When you do an xm save, does it automatically pause the domU and then
> > basically make a copy of the disk? 
> > 
> 
> No, it doesn't. Just try it. "xm save" will pause the guest, and then save the
> cpu and memory state to a file, and then stop the domain.
> 
> Later you can resume (restore) the guest from the save-file.
> 
> It doesn't do anything with the storage/disks.
> 
> > 3) I assume I  would expect the process to take the same amount of time
> > as a normal copy of the disk?
> > 
> 
> Yes. 
> 
> When the guest is saved/stopped, you can take a backup of the disks,
> and store the backup with the state/save-file.
> 
> -- Pasi
> 

Ok, now I understand. Just for background, I do look at each system as a
standalone system and we install backup software in many of them. If we
ever lost a file system or had a corrupted domU, it would be easier to
restore the domUs from a backup than rebuild and restore. 

That being said, I'm still struggling with what file system we should
run. We're using ocfs2 now, and we've had some corruption problems. The
above will work well for ocfs2, but it does take a while to copy a
sparse disk. 

If I were to run CLVM or LVM, I could save the state of the CPU/Memory,
but how would I backup the disk? Would it be any faster than using
sparse files?

What other file systems could I use? Again, my requirement is SLES11
with attached Xiotech SAN.

Thanks again.
James


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