Re: [Xen-users] is save and restore save?

[Harald Kubota <hkubota@xxxxxxx>]

Julian Hagenauer wrote:
> xm create myvm
> xm save myvm state.dat
> xm create myvm
> (now logging on an do some modifikations)
> xm destroy myvm
> xm restore state.dat
>
> Will that leave the filesystem consistent? Do i have a filesystem that is the 
> same like the one at the point of the saving?
> Is there a way to take a snapshot of a virtual machine for later staterestoring 
> instead of shuting the machine down and copying its imagefile?
>
>   
I thought about the same too and my conclusion was:

Since 'xm save' saves the memory and the state of the machine, but not 
the disk, any changes on the disk
and on swap space is bad.

However, if you do 'xm save', then do a snapshot from disks (including 
swap), then 'xm create' again
(which will have an unclean filesystem just like after a crash), then 
'xm destroy' and then undo all the
recent changes on disk and swap (undo snapshot), THEN you can 'xm 
restore' that state again.
Since memory is in the state.dat, and disk is unchanged (curtesy of lvm 
snapshots), that's ok.
That is, if lvm snapshots work as expected.

From what I gather on the web and several mailing lists, it's still 
marked as 'experimental' for a reason.
If you happen to have fancy hardware which can do snapshots in a 
reliable way, I see no problem.
Harald


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