On Sun, 2007-01-14 at 19:44 +0530, Ligesh wrote:
> On Sun, Jan 14, 2007 at 02:06:38PM +0100, Goswin von Brederlow wrote:
> > Ligesh <myself@xxxxxxxxxx> writes:
> >
> > > Sat, Jan 13, 2007 at 07:26:58AM +0530, Ligesh wrote:
> > > On Sat, Jan 13, 2007 at 12:57:04AM +0800, Tim Post wrote:
> > >> .. and incremental thereof, on a typical (classic) linux system.
> > >>
> > >> While I agree that lvm snapshots are the easiest way (now), if
> > >> developing something better, shouldn't a smaller option come into play?
> >
> > I'm assuming you want to make a snapshot without shutting down the domU.
> >
> > The problem with lvm snapshots is that xen does not pass down the
> > sync/suspend event from the dom0 to the domU. Normaly when you create
> > a snapshot from a mounted filesystem the fs gets asked to get itself
> > into a consistent state before freezing it. Not so with snapshoting in
> > dom0 and the filesystem mounted in domU. As a consequence mounting the
> > snapshot in dom0 can have filesystem errors, the mount can easily
> > fail.
>
> What I was proposing was a new option for xm, where it will be able to tell
> the domU to sync
> and suspend. We just need a domU kernel that will cooperate with this
> request. The problem with
> daemon is that a lot of checks and measures has to be in place to make sure
> that everything has
> happened as we thought it would, which in practice never happens anyway. If
> we can have a specific
> domU kernel that's aware of this feature, then it would provide almost 100%
> guaranteed consistency.
>
> Thanks.
Agreed. A daemon is a nice start (one that is very simple to install and
requires almost no configuration).. but a module is going to be the
goal.
Given our ability to do this at the kernel level, I think it would be
stupid NOT to.
A good starting point is think about what modules exist that would
provide a good basic building block, to keep us from re-inventing the
whole wheel. AoE comes to mind.
Best
--Tim
>
>
>
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