Re: [Xen-users] xen domU backups

[John Haxby <john.haxby@xxxxxxxxxx>]

Ferenc Wagner wrote:
> James Pifer <jep@xxxxxxxxxxxxxxxx> writes:
>   
>   
> > Can you back up individual domUs (img files) while they are running?
> >     
> Sure, but it will be an inconsistent backup.
>
>   
"Inconsistent" is an understatement.   The image file will be changing 
while you're backing up; you'll most likely end up with garbage in the 
parts of the guest file system that are even vaguely active while you're 
doing the back up.
> > Do you need to pause, make backup, un-pause?
> >     
> That helps, but the backup will still contain dirty filesystems.
>   
Sometimes it helps.   If you do a save-backup-restore that helps even 
more, but be aware that if you ever restore and start the backup then it 
will continue doing what it did at the time of the backup.  In fact, 
everything it had in progress at the time of the backup will be done 
again.   At the "mostly harmless" end of the spectrum you'll get mail 
messages that were in a queue re-sent; at the other end of the spectrum 
... Well, that depends on the applications.
You need the cooperation of those applications because you can't just 
blindly restore (and restart) the backed up domU image and hope that 
everything will be fine.
jch

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