Re: [libvirt-users] VM locking
On Mon, Aug 31, 2015 at 08:01:58PM +0000, Prof. Dr. Michael Schefczyk wrote:
Dear All,
I am trying to use VM (disk) locking on a two node Centos 7 KVM cluster. Unfortunately, I
am not successful.
Using virtlockd (https://libvirt.org/locking-lockd.html), I get each
host to write the zero length file with a hashed filename to the shared
folder specified. Regardless of which host I start a VM (domain) on,
they do produce the identical filename per VM. What does not work,
however, is to prevent the second host to start the VM already running
on the first VM.
Ok, so you've configured the locks to happen on a shared filesystem
which sounds correct.
My system is current Centos 7 using a gluster storage setup like
suggested
for oVirt (https://community.redhat.com/blog/2014/10/up-and-running-with-ovirt-3-5/)
based on the oVirt 3.5 repo but without an engine. I do this, because I
want to retain VM files in qcow2 format for live backups and with human readable
names. What does work then is, e.g., live migration. A locking mechanism to
prevent starting a VM twice would be good.
Ok, so you are using gluster for your qcow2 files.
Please note that this configuration - both according to redhat and
to my own trial and error - requires Lock=False in /etc/nfsmount.conf.
Is there a connection with my findings? My issues occur regardless
of the files being in NFS or Gluster folders. KVM must load the
Gluster storage indirectly via NFS rather than straight via Gluster,
as Gluster storage does not seem to fully work, at least in virt-manager.
I'm a little confused about whether the virtlockd lock directory is
stored on NFS or on GlusterFS at this point.
If using NFS though, the lock=false setting will definitely break
virtlockd. When you set lock=false, it means that any fcntl() locks
applications acquire are only scoped to the local host - no other
NFS clients will see them, which matches the behaviour you describe.
Regards,
Daniel
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