Running VMware Server on a Linux cluster

Hi

I'm looking to create a linux cluster using several old servers to specifically run VMWare (or any other virtualisation app). Any Ideas or pointers on this issue will be greatly appreciated.
The problem I'm having is that as far as i can tell VMWare Server will not run as a distributed process over all the nodes in the cluster at the same time, a virtual machine will only run on one computer at any one time.