Fwd: [Xen-users] differencing disks

[Alex Edwards <edwards.alex@xxxxxxxxx>]

---------- Forwarded message ----------
From: Alex Edwards <edwards.alex@xxxxxxxxx>
Date: Fri, Jul 9, 2010 at 9:40 AM
Subject: Re: [Xen-users] differencing disks
To: Bart Coninckx <bart.coninckx@xxxxxxxxxx>


yes I do believe that it is snapshoting, Differencing disks appears to be a msoft term given to their VHD tech. I could use snapshots but its more than I need. I want 1 point that i always go back to. Could I create a system image that can just be remounted when I want to go back? If i had an image of my system at a point in time, how fast could I remount it in a different VM?

thanks
Alex

On Fri, Jul 9, 2010 at 9:03 AM, Bart Coninckx <bart.coninckx@xxxxxxxxxx> wrote:

On Friday 09 July 2010 09:29:09 Alex Edwards wrote:
> hello all,
>
> I have little experience of virtualisation only what i have read in the
>  past couple of days! but i think it can offer me what i need. I would be
>  grateful for your input.
>
> I have 3 systems I need to demo, I want to deploy these systems to a base
> state where i know that they will be working. At this point I want to lock
> them. I want to be able to give it at this point to somebody and say "do
> want you want" when/if they break it i want to be able to return it to its
> known stable state. This return to a stable state needs to happen quickly,
> seconds would be great but minutes would be acceptable.
>
> I have been reading about differencing disks and believe that these would
>  be the right solution?
>
> thanks
> Alex
>

I believe that is a sort of snapshotting you are referring to; AFAIK Xen does
not have such a feature, but LVM does. You need to install your root file
system on LVM as well, don't know what the effect would be of restoring a root
file system snapshot however. Also don't know if this can be done in "seconds"
- you need to try this I think. Another way could be to make a RAID1,
disconnect it after your initial install, then after changes swap the main
disk and mirror it again to the first one to get to the original state. This
answers the "in seconds" part.

B.

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