Re: [Xen-users] Save/Restore/Reboot FS Corruption

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

Hrrrmm.  Sounds nasty :-(

> I've been looking for information about this matter, but didn't found
> too much.
>
> Saving and restoring works pretty good, but the problem comes when I
> reboot after
> restoring. FileSystem becomes corrupt after the restoration, so it
> enters "read only"
> status.
>
> Can't provide more info, since I'm far from the computer, only thing I
> can say, its a Debian Etch debootstraped VM, with a ext3-fs.
> The disk image of the VM is stored on a remote storage device, so the
> directory containing the image is mounted via NFS.
>
> Is anyone else experiencing this issue?

What was the sequence of operations that you went through when this happened?  
Something like:

xm save <domain>
... time passes ...
xm restore <domain>
... reboot domain ...
... corruption!

Is it possible that anything modified the domain's virtual disks during 
the "... time passes ..." section above?  Like maybe somebody mounted a 
filesystem in the virtual disk from dom0 for some reason?  Or if somebody 
accidentally did an xm create in the meantime?

Domains will, unfortunately, typically corrupt their virtual disks if their 
filesystem changes whilst they're suspended.  You might not notice this until 
the filesystem gets mounted at reboot time.  Linux doesn't generally expect 
data to change on a disk it thinks it has mounted - even if it's actually xm 
saved at the time - and it can get confused if changes do occur.

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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