Re: [linux-lvm] has anyone used LVM in a HA cluster?

[Austin Gonyou <austin@coremetrics.com>]

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From what I understand you *can* mount the LVM volumes on multiple hosts
at the same time, but you should be *readonly* on the hosts which do not
*own* the data on the disks. You could then *remount* the volume on the
target failover host. 
The only draw back is you will need to have monitoring, in the end
anyway, that will allow you to see:

1. What hosts have what volumes mounted
2. and in what mode(ro/rw?)

Also, you would need to use a filesystem that supports:

1. multiple hosts mounting it
2. filesystem 'remount' option

Talk to the guys on the Linux FailSafe list, they might be able to help
point you as well.

On Fri, 2002-05-10 at 02:26, Patrick Caulfield wrote:
> On Thu, May 09, 2002 at 09:54:40AM -0700, Au, Richard wrote:
> > Hi,
> > 
> > I'm wondering if anyone has used LVM in a high-availibility
> cluster
> > where two servers are connected to shared storage (the physical
> > volumes).  If so, which cluster solution did you use?  Will there
> be
> > problems if the logical volumes are visable to both servers, even
> if
> > only one of them has them mounted?  Thanks!
> 
> Provided you're either using GFS as the file system or being VERY
> careful to
> mount the filesystem on only one node at a time you can do this.
> 
> The key is just to be VERY careful. If you need to do any LVM
> commands you MUST
> 
> umount filesystems on all other nodes
> vgchange -an on all other nodes
> 
> do the LVM metadata changes
> 
> vgscan on all nodes
> vgchange -ay on all nodes.
> 
> The safe thing to do is to have only one node have the LVM commands
> available to
> it (apart from vgscan & vgchange) and be VERY careful.
> 
> I'll say that again: Be VERY careful !
> 
> patrick
> 
> 
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-- 
Austin Gonyou
Systems Architect, CCNA
Coremetrics, Inc.
Phone: 512-698-7250
email: austin@coremetrics.com

"One ought never to turn one's back on a threatened danger and 
try to run away from it. If you do that, you will double the danger. 
But if you meet it promptly and without flinching, you will 
reduce the danger by half."
Sir Winston Churchill

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