[CentOS] Sharing RAM between VM

Thank you, for all your answers!

What about the other question? Can clustering help in completing this
task? I thought cluster nodes are sharing RAM on default ( obviously I
was wrong).

>From your answers I'm getting to think that best decision for this task,
in my case, is to buy some RAM. I'm not going to make more VMs. Their
number will stay constant.

nate, which vmware you use? VMware ESXi or VMWare Server or something
else?

Thanks, again for your help!

p.s. Stable xen, has ballooning. You can say for every VM:
memory=1024MB, max-mem=2048MB. And you can tweak the memory "manually",
without having to restart the VM and without any other problems.