Re: [Xen-devel] sharing file between running domU (windowxp) and dom0

[Pradeep Singh <rautelap@xxxxxxxxx>]

On Fri, 7 Dec 2007 16:48:24 +0000
Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:

[snip]
> 
> You should never, ever do that.  You *must always* shut down a domain
> before modifying its filesystem from the outside.  Otherwise you can
> create corruption that will destroy the domain's disk data.  Just
> pausing the domain or saving it is not enough to protect you, and
> neither will using the guest's "hibernate" feature.  The domain
> *really* has to be properly shut down.

Mark,I guess i understood your point here.
My question is what about cluster filesystems like GFS or OCFS2.
Does virtual environment outs some extra constraints on the filesystems?
FWIW how is XenFS different from OCFS2 and GFS?
What i mean is how is a HVM domain(e.g linux) and domain0 different
from two machines on a network from the perspective of cluster
filesystems?

PS - I am a rookie as far as distributed/cluster fs are
concerned.Please spare my ignorance and kindly enlighten me on this.

Thanks
        Pradeep
> I'm sorry to emphasize that so harshly but it really is very very
> important.
> 
> This is because filesystems are written with the assumption that they
> "own" the disk and that nothing will ever change "underneath" them.
> If you modify the filesystem from the outside then you're doing stuff
> without the guest OS knowing about it.  It won't be looking for this
> and will get confused.  This could seriously damage your filesystem.
> 
> If you do it by accident, you could try xm destroy-ing the domain
> immediately in order to prevent it getting confused by the changes to
> the underlying disk - before it has time to corrupt anything.  xm
> destroying a domain which is modifying the filesystem has corruption
> risks of its own though (and will lose any in-memory data), so it's
> better just to avoid this situation.
> 
> I hope that helps.  Again, sorry to be so harsh, but this is one
> thing about virtual machines that is *really* important to watch out
> for, or you will have major problems at some stage.
> 
> Cheers,
> Mark
> 


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