Hi all,
I have a question about NFS datastore and unsafe migration.
When migrating a virtual machine having a virtio disk in writeback cache
between two hosts sharing a single NFS datastore, I get the following error:
"Unsafe migration: Migration may lead to data corruption if disks use
cache != none or cache != directsync"
I understand why libvirt alerts for unsafe migration in cases where no
coherency is enfoced by the underlying system; however, is it really the
case for nfs?
From what I know (and from the man page), by default nfs has
open-to-close consistency, which seems quite right for migrating a
virtual machine between (as only one host at a time reads/writes/locks
the virtual disk files).
I know that I can simply use cache=none to let the problem go away;
however, this significantly impairs performance when used on nfs.
Am I missing something?
Thanks.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8
