> Depends what your goal is, if you want to run a cluster with shared > memory between systems, you typically need a very high speed interconnect > and very low latencies, your not likely to achieve this within VMs. > > Your original message just talked about sharing ram between VMs, you > didn't mention why you were specifically interested in doing that. > > > nate, which vmware you use? VMware ESXi or VMWare Server or something > > else? > > Whenever possible I'd use ESXi, I happen to use vmware server on > the system that is sending my email because it's old and ESXi doesn't > support the 3ware 8006-2 SATA card in it. Check the hardware > compatibility list, the list is fairly short for some things like SATA, > though ESX 4 is due out in the coming week(s) which is supposed to > dramatically improve SATA support. > > Note that out of the box ESXi(with the free license) doesn't support > snapshots or cold migrations(between servers) at least last time > I checked the feature comparisons sheet. I'll be installing about > 12 new ESXi systems soon. VMware server does not support page > sharing or memory ballooning, and does support snapshots. I use > vmware server 1.x, probably will go to 2.x in the next couple months. > nate, thanks a lot for this answer. I'll give ESXi a try. (Maybe I'll wait till next version) > > 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. > > That's not memory ballooning, at least not in the vmware world, and > you can do the same in vmware, though if you decide to drop the > amount of physical memory allocated to the guest without having the > guest free up that memory you'll go into swap pretty quick, so it's > not a practice I do, really ever. > > If Xen has a specific balloon driver like vmware and inflates the > balloon when you change the memory settings that would be pretty > cool, as far as I know vmware does not do that, the balloon only > kicks in when host memory is low, not when you decide you want to > resize the guest.