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.
The additional layer of caching will result in inconsistency because iSCSI doesn't have a mechanism to provide cache coherence between two nodes.
Regards, Anthony Liguori
#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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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