[Linux-cluster] cluster between 2 Xen guests where guests are ondifferent hosts

[Jeff Sturm]

Santosh,

The hosts are responsible for fencing the guests, so, as far as I know
it is not possible to use fence_xvm without also configuring fence_xvmd.

In our configuration we run an "inner" cluster amongst the DomU guests,
and an "outer" cluster amongst the Dom0 hosts.  The outer cluster starts
fence_xvmd whenever cman starts.  The fence_xvmd daemon listens for
multicast traffic from fence_xvm.  We have a dedicated VLAN for this
traffic in our configuration.  (Make sure your routing tables are
adjusted for this, if needed--whereas aisexec figures out what
interfaces to use for multicast automatically based on the bind address,
fence_xvm does not.)

If your Dom0 hosts are not part of a cluster, it may be possible to run
fence_xvmd standalone.  We have not attempted to do so, so I can't say
whether it can work.

Jeff

> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of 
> Panigrahi, Santosh Kumar
> Sent: Friday, October 24, 2008 7:59 AM
> To: linux clustering
> Subject: [Linux-cluster] cluster between 2 Xen guests where 
> guests are ondifferent hosts 
> 
> Hello,
> 
> I am using RHEL5.2+RHCS and configured a 2 node cluster in 
> XEN virtual environment for testing purpose only. These 2 
> cluster nodes are 2 virtual guests (p6pv1, p7pv1) and each 
> virtual guest is on different hosts/ Dom-0s (p6 & p7). I have 
> already gone through the older questions on this forum with 
> similar problems and also the wiki page 
> (http://sources.redhat.com/cluster/wiki/VMClusterCookbook ).
> But still I have confused a bit regarding the Xen fencing in 
> this scenarios.
> I don't want to do any live migration here and only to do a 
> failover/failback services between 2 cluster nodes. I want to 
> know whether I have to configure fencing only between the 2 
> guests (using
> fence_xvm) or also between the 2 hosts (using fence_xvmd) as 
> well, where as my cluster nodes are 2 Xen guests.
> 
> I am configuring the cluster using luci and there options are 
> as follows.
> 
> Fence Daemon Properties:
> Post Fail Delay		- 0
> Post Join Delay		- 3
> Run XVM fence daemon	- tick mark selected
> 
> XVM fence daemon key distribution:
> Enter a node hostname from the host cluster			- ?	
> Enter a node hostname from the hosted (virtual) cluster	_ ?	
> 
> Can someone please help me in this regard?
> 
> Regards,
> Santosh
> 
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