Corrupted filesystem, possible after livemigration with iSCSI storagebackend.

Corrupted filesystem, possible after livemigration with iSCSI storagebackend.

[Espen Berg]

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>

#virsh version
Compiled against library: libvir 0.7.6
Using library: libvir 0.7.6
Using API: QEMU 0.7.6
Running hypervisor: QEMU 0.11.0

#uname -a
Linux vm01 2.6.32-bpo.2-amd64 #1 SMP Fri Feb 12 16:50:27 UTC 2010 x86_64 
GNU/Linux

Regards
Espen