Thank you for replying, Vladislav!
I think the problem should be unrelated to iSCSI, you have correct setup
(of course I did not thoroughly look through all info, but idea is
perfectly correct).
Thank you for confirming.
Did you turn caching off for your VMs disks?
That's a point. Indeed caching was not explicitely turned off and I just
noticed that the default setting of the cache attribute of the device
tag in libvirt has changed. [1]
I would expect that libvirt flushes all caches before finalizing the
migration process. But it is probably best to turn off caches anyway.
I have now configured:
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source dev='/dev/mapper/1p-lun1-vm_disk'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x0'/>
</disk>
Unfortunately the problem persists :-(
(To check i run a loop of dd commands while migrating the vm,
restarting iscsi initiators and iscsitargets. I still get errors in the fs.)
I have configured iSCSI timeouts rather short (noop_out_timeout 5
seconds) and "no_path_retry queue" on the multipath device.
My question(s):
1) Is it conceptually wrong what I am trying to accomplish?
No, I use almost the same setup in production. Except I use IET and I
have cLVM on top of luns.
Good to hear. Could the use of cLVM make a diffenrence (since this layer
is cluster aware)?
5) Is TGT multipath capable?
Multipathing is much more an initiator concept, so I cannot see how
target side may affect that (unless it has some serious flaws with
reordering).
I think so also, but was a bit irritated that at the webpage of another
implementation (istgt, [2]) it is explicitly mentioned that it is
multipath capable.
Thanks for your help so far,
Sven
[1] http://libvirt.org/formatdomain.html#elementsDevices
[2] http://www.peach.ne.jp/archives/istgt/
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