Re: [Xen-users] small cluster storage configuration?

[John Madden <jmadden@xxxxxxxxxxx>]

> GlusterFS also does replication - question is whether it's performance
> is up to supporting VMs.  Mixed responses so far, some suggestions that
> this is supposed to get a lot better in version 3.3 (currently in
> beta).  Not sure the impact of Red Hat's acquisition of Gluster.
I used GlusterFS a couple of years ago for a storage project and it 
worked very well until we put load on it.  There were multiple problems 
with our implementation though:
- It was an older version of Gluster.
- I only had two nodes.  No striping, just mirroring.
- The backend storage was 7200RPM SATA SAN space and thus slow.  Both 
nodes shared the same spindles.
- I was stingy on RAM for the storage nodes.
- The primary application was a PHP session store that handled in the 
neighborhood of 600 requests per second.  That's a lot of read and write 
for this sort of system.  Keep in mind the FUSE layer...
We moved to a single-node of NFS to replace this and even then had to 
move the underlying storage to an FC zone of the SAN to patch up 
performance.  My understanding of GlusterFS is that it's better designed 
to handle larger files and this may make it a better candidate for 
hosting VM's.
I'd still be concerned about only having 16 drives but I think it's 
worth a shot.  RAID them all at the host level, hand the (ext4 or better 
-- I'd skip ext2/3) filesystem to Gluster, then stripe+replicate.  Do a 
whole bunch of testing.  Live migration won't be a problem but 
performance might be.
John




--
John Madden / Sr UNIX Systems Engineer
Office of Technology / Ivy Tech Community College of Indiana

    Free Software is a matter of liberty, not price. To understand
    the concept, you should think of Free as in 'free speech,' not
    as in 'free beer.' -- Richard Stallman

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