Fedora xen - Nov 2006 - Need some setup pointers for using Xen in a HA system

Hello to everyone on the list.  We''re looking at making our datacenter
monitoring system (traffic graphs, nagios, etc) run under Xen so a
machine failure doesn''t kill off our entire monitoring system.  Right
now, all our monitoring runs on a single machine, so if that fails,
we''re dead in the water, which is why we want to do this.

Here''s what we''ve thought of so far.

2 identical machines running Xen-enabled
All monitoring services running within domU
Shared filesystem provided by GFS (Sun T3 array connected to both
machines with a brocade switch)
domU root filesystem is a loopback-style EXT3 on the GFS filesystem

The sticky point is getting set up so that we can move the domU from
one machine to the other in a live migration scenario, or activate on
the other machine in the case of a crash.  In the second case (crash),
we''d like to automate the process so it will automatically come up
properly.

The distro in use for both dom0 and domU is planned to be FC6.  Can
any of you who have done this type of thing in a real-life scenario
think of anything I''ve missed, or any issues with what we''re
thinking?
 Especially suggestions for automating in the case of a crash would be
welcome!

Thanks for any input any of you can give!

Jeremy