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Re: [Xen-users] Sharing space on a SAN?

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Sharing space on a SAN?
From: Peter Van Biesen <peter.vanbiesen@xxxxxxx>
Date: Mon, 8 Sep 2008 17:23:15 +0200
Cc: Maximilian Wilhelm <max@xxxxxxxxxxx>
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We tested that too. It is overkill and degrades performance.

Simply attach the raw lun's to your domu ( /dev/disk/by-id ) and allow all you 
dom0's to see them. live migration works perfectly then.

A little warning : every lun should only be allowed to be accessed by 1 domu or 
dom0, unless the filesystem on it is able to handle multiple systems. Booting 
your domu on two systems on the same lun will result in massive datacorruption.

We have been using this setup for over a year now and had no problems 
whatsoever - provided you check every domu has only been started once AND every 
lun is attached to only one domu ( typo's can happen ). We're using a simple 
script to check all that before we start a domu. There are also a lot of xen 
linux clustering projects around that can help you, just google them. 

Kindest regards,

Peter.

On Thursday 04 September 2008 16:34:39 Maximilian Wilhelm wrote:
> Anno domini 2008 James Pifer scripsit:
> 
> > I have several SLES 10 SP1 xen servers. Right now each one has it's own
> > internal disks, or has space on our SAN. I would like to be able to xm
> > migrate VMs between my xen servers. Everything I've read so far talks
> > about all the xen servers having network access to the VMs. 
> 
> > Is it possible to use a SAN for this? We can assign the same vdisk to
> > multiple hosts, but not sure what would be required on the dom0's to all
> > use the same disk for storage of their domU's. 
> 
> > We do something similar with oracle, where we have a cluster of linux
> > machines, but from what I've gathered Oracle does something special
> > allowing all the systems to share the data vdisk. I was not part of that
> > installation, so I'm not sure exactly how it's setup.
> 
> > Anyone know if sharing a virtual disk on a SAN is possible with xen?
> > What's required to make it work?
> 
> Sure.
> Have a look at CLVM and/or EVMS.
> 
> If you are using image files file systems like GFS an OCFS2 maybe
> interesting, too.
> 
> Ciao
> Max



-- 
Peter Van Biesen
Sysadmin VAPH

tel: +32 (0) 2 225 85 70
fax: +32 (0) 2 225 85 88
e-mail: peter.vanbiesen@xxxxxxx
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