CentOS virt - Aug 2008 - Shared Storage Options

Hello all.

I would like to canvas some opinions on options for shared storage in a Xen
cluster.  So
far I've experimented with using iSCSI and clvm which mixed success.

The primary concern I have with both of these options is that there seems to be
no obvious
way to ensure exclusive access to the LUN/device to the VM I want to run.  On a
couple of
occasions during my playing I've accidentally started the same VM on two
servers and
corrupted the said filesystem.

I've tried setting up GFS but I don't think I'm smart enough to do
that.  The fencing has
me baffled.  In fact fencing had me baffled with clvm but I somehow managed to
trick it
into working though probably not how it's supposed to.

I'd be happy to persist with either of the above methods if I could work out
how to lock
the device.  Can anyone offer some advice?

Regards
Brett Worth

Jerry Ablan wrote:
> Has anyone played with OCFS2?
> 
> http://oss.oracle.com/projects/ocfs2/
Thanks for suggesting this.  I've done a fresh install of CentOS 5.2 and put
OCFS2 on top.
  Its really easy to use and install and the the performance looks really good. 
I'm going
to be using OCFS2 for a few more applications from now on.

Meanwhile...

Once I ran up Xen on these machines I was able to use file based storage
allocation to the
VMs and have it running with reasonable performance.

My original problem is still there however.  I've tested the flock
functionality of OCFS2
and it works but Xen it seems doesn't do locking even on a shared
filesystem.  It is
possible that Xen is trying to do some other sort of file locking but
unfortunately OCFS2
only supports flock.

I could write some scripts to replace xm which could check for the existence of
a lock
file before attempting to start a VM but that seems a bit clunky.

Is there a proper way to do this?

Regards
Brett
> -----Original Message-----
> From: centos-virt-bounces at centos.org [mailto:centos-virt-bounces at
centos.org]
> On Behalf Of Brett Worth
> Sent: Thursday, August 21, 2008 6:22 AM
> To: Discussion about the virtualization on CentOS
> Subject: [CentOS-virt] Shared Storage Options
> 
> Hello all.
> 
> I would like to canvas some opinions on options for shared storage in a Xen
> cluster.  So
> far I've experimented with using iSCSI and clvm which mixed success.
> 
> The primary concern I have with both of these options is that there seems
to
> be no obvious
> way to ensure exclusive access to the LUN/device to the VM I want to run.
> On a couple of
> occasions during my playing I've accidentally started the same VM on
two
> servers and
> corrupted the said filesystem.
> 
> I've tried setting up GFS but I don't think I'm smart enough to
do that.
> The fencing has
> me baffled.  In fact fencing had me baffled with clvm but I somehow managed
> to trick it
> into working though probably not how it's supposed to.
> 
> I'd be happy to persist with either of the above methods if I could
work out
> how to lock
> the device.  Can anyone offer some advice?
> 
> Regards
> Brett Worth