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Simon Waters wrote: > In that XEN provides a "virtual x86" server for the guest OS. Of course > it then does clever stuff to step out of the way as much as possible to > minimize the overhead of virtualization. But it still breaks stuff > enough to require guest OS changes, so not a simple x86 emulator. Depends on the processor in use. Where the processor supports virtualisation in hardware, the user domain operating system doesn't need any special support. In xen terminology, this is "full virtualisation". Where the processor doesn't, you need co-operation from the user domain OS. This is "paravirtualisation". Xen itself partitions domains from each other, but doesn't handle everything itself -- network access for instance is (by default) bridged onto the physical hardware by the master domain. Neither does it provide a virtual machine in quite the same way that, say, VMware does. You don't get the BIOS emulation, you get dumped straight into the OS boot when you start a new xen domain. Each domain also runs directly on the CPU and has access directly to it's own chunk of physical RAM that is assigned to it alone and can't be paged out by some other external process. James -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html