[CentOS-virt] Virtuozzo & GFS

Sat May 31 20:19:55 UTC 2008
James Thompson <james at ubercart.org>

I believe both dlm_send and dlm_receive are part of GFS' locking mechanism
where locks are bouncing back and forth between servers. The Zimbra VE is
pretty consistent in its internal load and what struck me was that
Virtuozzo's PIM interface flags the increased load (leading me to believe it
is abnormal). Perhaps I am mistaken on the meaning of the load figures
though. On a busy machine what would be considered a normal load? Does it
differ based on the number of processors and cores available in the system?
I came across this article which makes me think I may be mistaken in my
concern: http://www.linuxjournal.com/article/9001

Can anyone who is using GFS perhaps comment on how it has performed for them
in virtualization scenarios? When initially working with just the iSCSI
mounted disks involved operations were just slightly less "snappy" than
local file operations. With GFS things seem at least noticeably more
sluggish which I expect is normal given the multi-server locking but has
anyone worked on optimizing GFS performance in a virtualization environment?

James Thompson

On Sat, May 31, 2008 at 11:56 AM, Scott Dowdle <dowdle at montanalinux.org>

> James,
> ----- "James Thompson" <james at ubercart.org> wrote:
> > I have just finished deploying two Dell PowerEdge 1950s with CentOS
> > 5.1 and Virtuozzo 4. GFS is up and running and Virtuozzo is configured
> > for shared-storage clustering. Everything works adequately but I am
> > wondering if anyone else has experienced load issues like I am seeing.
> > I have three VEs/VMs running, two on one node and one on the other
> > node. One of the VEs on each node are doing very little (one is just
> > idling with apache and mysql and the other is running rsync every six
> > hours). The other is running Zimbra. Every so often load will spike on
> > the node running the Zimbra VE to as high as 2 or 3 then settle down a
> > short while later to around 0.8 or 0.9. During the spikes the node not
> > running Zimbra will other see an increase from its idle load of 0.4 or
> > so up to as high as 1.7 as I have seen. I notice when running top that
> > dlm_send and dlm_recv will jump to the top fairly frequently when
> > these load spikes occur.
> >
> > What I am wondering is whether anyone else has experienced these kind
> > of load scenarios with GFS and what they have done to deal with them?
> > We are hoping to deploy a bit more densely on this setup so I'd like
> > to make any performance adjustments I can at this stage.
> >
> > Thanks,
> > James Thompson
> A load of 2-3 isn't much at all... so I don't think I'd call that much of a
> spike.  I have run OpenVZ at work and on a hobby server.  In both cases I
> have about 7 containers... one of them being Zimbra.  The other 6 containers
> are fairly busy so the two machines see a decent amount of load.  I am NOT
> using GFS though.  What is dlm_send and dlm_recv part of?  GFS?
> TYL,
> --
> Scott Dowdle
> 704 Church Street
> Belgrade, MT 59714
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