[CentOS] does anyone have experience with clusters?

[Kwan Lowe]

>  I have used Linux Heartbeat to failover a MySQL cluster before, and
>  it's actually been running very well for about 3 years now. But, I
>  want to start looking @ total clustering, with DRBD - where everything
>  (not just MySQL) is being replicated across the 4 machines. I'm also
>  intereated in load balancing.

 > The cluster will be running / hosting a few XEN Virtual Machines, and
 > idealy if one PC / server dies (hardware failure / power failure /
 > etc), then on of the other machines should still be running the
 > virtual machines, i.e. no downtime. Is this possible? Can somone steer
 > me into a direction where I can get more info on this?

I've done some similar types of setups:

1) The first setup included two physical machines running separate Xen
VMs with the critical data on a DRBD store:  Setup was quite easy
using docs for DRBD and HA on the HowtoForge site.  No difference in
using the Xen environment except that I used a second NIC instead of a
serial cable. Works great for a webserver. I was also running the
CentOS directory server with this setup until I got replication
working.

2) Second setup was to place the heartbeat on the physical machines.
On failure, it would autostart the Xen VM.  It worked, but was a PITA
to get right. The reason to do this was to only use resources when the
machine failed, rather than allocating the 1G constantly.

I'm currently trying to get live VM migration running under Xen.