[Ocfs2-users] OCFS2 for store Xen VM image

[Daugherity, Andrew W]

On May 15, 2012, at 10:28 AM, Alessio Cecchi wrote:

> I would like to use an OCFS2 (1.4 on CentOS 5) file system for store Xen 
> VM image.
> 
> Could be a good idea? There may be performance issues? The VM will be 6 
> or 8 with low I/O.
> 
> By using OCFS2 (in my configuration the backend device is DRBD) I will 
> able to switch from one Xen host to other simple.



We used to do this and I would not recommend it.  Performance was lousy and reliability wasn't great either, and ocfs2 was the #1 cause of downtime for us.  This was in the OCFS2 1.2 series, on openSUSE 10.2 and later 10.3.  Things have improved, bugs fixed, etc., but performance still lags compared to an LVM solution.  VM storage isn't really a good use case for a clustered FS in general, as only one VM host should be accessing a VM image at a time anyway, so putting the VM store on NFS would probably perform better than ocfs2.  (I haven't tried that with Xen, and NFS definitely has its own set of issues, but it's worked well for us with VMware.  I still prefer Xen + clvm though.)

Now we use the pacemaker cluster (on SLES 11 SP1 + HAE) for our Xen VM cluster.  VM storage is on clustered LVM (clvmd) where each VM has its own LV, and performance and reliability are both much better.  We do still use ocfs2 for a small "management" FS where we store the VM config files and the Xen locking dir, but it's managed by pacemaker rather than using its own heartbeat stack.

-Andrew