[nSLUG] XEN & Heartbeat

Stephen Gregory nslug at kernelpanic.ca
Wed Jun 3 22:36:55 ADT 2009

I use VMware ESX on about a dozen machines with and without SAN. I have
not used XEN recently but there a couple of best practises for VMware
that likely apply. The big one is buy more network cards. You can easily
use three or more nics per machine. Generally you want to:

Separate host management traffic from virtual machine (guest) traffic.
Separate storage traffic from everything (very important!).
Separate live migration traffic from guest traffic and preferably
management traffic. (Does XEN support a dedicated port for live migration?)
And it is always nice to have a backup storage network.

When using virtual machines for HA, allocate ram to guests such that you
are able to live migrate everything to one machine. It seems obvious but
I have seen more then a few cases where it wasn't possible to live
migrate all the guests to one host because RAM was over committed. If
you don't need strict HA and are more interested in hardware
consolidation then you can reconfigure the virtual machines with less
RAM before restarting on second host.

Beware of virtual machine creep. A common problem is having too many
virtual machines because VMs are easy to deploy.


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