Re: Fwd: Corrupted filesystem, possible after livemigration with iSCSI storagebackend.

["Daniel P. Berrange" <berrange@redhat.com>]

On Mon, Mar 15, 2010 at 08:59:10AM -0500, Anthony Liguori wrote:
> On 03/15/2010 08:46 AM, Espen Berg wrote:
> >In our KVM system we have two iSCSI backends (master/slave
> >configuration) with failover and two KVM hosts supporting live migration.
> >
> >The iSCSI volumes are shared by the host as a block device in KVM, and
> >the volumes are available on both frontends.  After a reboot one of the
> >KVMs where not able to start again due to file system corruption.  We
> >use XFS and have problems to understand what caused the corruption.
> >
> >We have ruled out the iSCSI backend as both the master and slave data
> >where consistent at the time.
> >
> >Anyone else had similar problems?  What is the recommended way to share
> >an iSCSI drive among the two host machines?
> >
> >Should XFS be ok as a file system for live migration?  I'm not able to
> >find any documentation stating that a clustered file system (GFS2 etc.)
> >is recommended.  Are there any concurrent writes on the two host
> >machines during a livemigtation?
> >
> ><disk type='block' device='disk'>
> ><driver name='qemu'/>
> ><source dev='/dev/disk/by-path/ip-<ip>:3260-iscsi-test2-lun-0'/>
> ><target dev='sda' bus='scsi'/>
> ><address type='drive' controller='0' bus='0' unit='0'/>
> ></disk>
> 
> You need to use cache=off if you've got one iscsi drive mounted on two 
> separate physical machines.

FYI, this can be done by changing the disk XML driver

  <driver name='qemu'/>

to be

  <driver name='qemu' cache='none'/>

Regards,
Daniel
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