Ruslan Sivak <russ at vshift.com> writes: > > running vmware under a xenU guest wouldn't lift any ram limit > > imposed by the xen kernel or dom0. ... > The 4GB limit is artificial, and only applies to the vm's started > using their closed source XenSource. The host OS is most likely > CentOS 5, and sees the whole 8GB (although it's not x64, so I'm > guessing they use PAE or something.) It is PAE. > I only need 8GB of ram support, and no other features that are offered > in XenStandard, so it seems kind of a waste to pay $1k per server for > that. If another virtualization technology was installed on that OS, > you can get the use of the other 4GB, and if not, I can always run my > apps on Dom0, although I'd prefer to not install too much stuff on > Dom0. First, The Dom0 OS runs as a guest of the Xen hypervisor- it is just a guest that happens to have access to the PCI bus as well. The Xen hypervisor still controls what ram and CPU all domains including the Dom0, can see; if the xen kernel is limiting you to 4G ram total, that limit will apply in the Dom0 as well. Also, you are not going to be able to run a virtualization technology that uses the hardware virtualization support from within a Xen guest, even if that Xen guest happens to be the Dom0. The Xen hypervisor controls access to those instructions. You can run virtualization technologies that don't require HVM- OpenVZ and linux vserver will both work fine. Heck, you can do that within an unprivileged Xen DomU, but that won't help you if you want to run windows.