[Linux-cluster] RHEL 6 cluster filesystem resource and LVM snapshots

[Jankowski, Chris]

Xavier,

I do not think that I have to use CLVM with ext4 or XFS in a cluster.

The ext4 or XFS filesystems will be on shared (FC) storage, but they will be presented as a filesystem resource i.e. accessible to only one cluster at a time, as they have to be. So, I believe that simple LVM will do and snapshots will be available.

The question is about the coexistence of a snapshot and the cluster filesystem resource. For example, what will happen if the node that runs the resource and happen to have created and mounted a snapshot on it, fails?

I need to integrate snapshots for backup and keep the system highly available during backup as well.

Regards,

Chris Jankowski

-----Original Message-----
From: linux-cluster-bounces at redhat.com [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Xavier Montagutelli
Sent: Tuesday, 23 November 2010 21:18
To: linux clustering
Subject: Re: [Linux-cluster] RHEL 6 cluster filesystem resource and LVM snapshots

On Tuesday 23 November 2010 07:13:56 Jankowski, Chris wrote:
> Hi,
> 
> I am preparing a build of a RHEL 6 cluster with a filesystem resource(s)
>  (ext4 or XFS).  The customer would like to use LVM snapshots of the
>  filesystems for tape backup.  

Where will your filesystem resource be located ? In a cluster, it's usually on 
a shared storage, using *cluster* LVM. Are snapshots available now with CLVM ? 
It was not the case last time I read documentation, which is/was (?) a serious 
drawback.

>  The tape backup may take a few hours after
>  which the snapshot will be deleted.
> 
> Questions:
> 
> 1.
> Is the filesystem resource compatible with using LVM snapshots?
> 
> 2.
> How can I reconcile the temporary existence of a snapshot with the notion
>  of the filesystem resource, which is all about having things permanently
>  mounted ?
> 
> 3.
> Would either ext4 or XFS be preferable for any reasons for use with
>  snapshots for backup?
> 
> I'd appreciate your comments.
> 
> Thanks and regards,
> 
> Chris Jankowski
> 

-- 
Xavier Montagutelli                      Tel : +33 (0)5 55 45 77 20
Service Commun Informatique              Fax : +33 (0)5 55 45 75 95
Universite de Limoges
123, avenue Albert Thomas
87060 Limoges cedex

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