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Re: [Xen-users] migration, shared storage and fencing

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] migration, shared storage and fencing
From: Bart Coninckx <bart.coninckx@xxxxxxxxxx>
Date: Fri, 13 Aug 2010 14:50:08 +0200
Cc: David Heidt <david@xxxxxxxxxxxxxxxx>
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On Friday 13 August 2010 14:18:34 David Heidt wrote:
> Hello List,
> how do you guys manage the following scenario:
> two host Dom0s: Alice and Bob with shared SAN (fibre)
> one DomU: Chalie. Charlies filesystem resides on the shared storage.
> * Charlie is running per default on Alice
> * Alice is shutting down for maintainance and ist automatically
> (heartbeat) migrating Charlie live to Bob
> * Charlie is now running on Bob
> * Alice is returning
> * The foolish admin types on Alice's shell: "xm crea Charlie.cfg" ->
> Charlie possibly broken, at least unusable!
> My idea was to write a wrapper script for xm to check first, if Charlie
> is already running on the partner Node and, if so, offering live migration.
> In my first try I wrote a script that checked 'xm list' on the remote
> host via ssh. But I don't want to rely on ssh, nor do I want to leave
> unprotected ssh-root-keys on the servers.
> My idea is to ask the xend-relication-service for running DomUs. Can
> this be done somehow from the shell?
> Cheers,
> David
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Why not let clustersoftware take care of starting and migrating Xen DomU's. 
Pacemaker has an excellent resource agent for that and it allows you to choose 
preferred nodes and stuff. Of course, everything needs to be done via the 
cluster manager software, no more manually doing "xm ..." because that would 
confuse the cluster. I have this running and it works perfectly. It needs a 
little bit of scripting for backups (we shut DomU's briefly down for that and 
don't want them to come up until the snapshot has been taken). 


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