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Re: [Xen-users] para- and full-virtualization on same system?

   Based on a few of the follow-ups, I wanted to add some detail:
     all the machines could be headless (only command-line access is
   we may need real machines for Windows and MacOS if their
can't be turned off


   Kent Watsen wrote:
Can I consolidate all my servers to one machine - here are my current machines:
         OpenBSD (used for external services: dns, http, smtp)
     OpenBSD (used for internal services: dns, http, smtp, imap,
smb, nfs, svn, bugzilla)
     OpenSBD (used for upgrading either of the above servers
any downtime)
           OpenBSD (used as a build/test machine)

These would need to run in an HVM (full virt) domain, since OpenBSD doesn't have support for Xen. I'm not sure it's as well tested as Linux / Windows under HVM, though,

     FreeBSD (used as a build/test machine)
     NetBSD (used as a build/test machine)
     RedHat (used as a build/test machine)
     CentOS (used as a build/test machine)
     SuSE (used as a build/test machine)
     Solaris (used as a build/test machine)

Linux 2.6-based distros can run in paravirt mode. Support for FreeBSD, NetBSD and Solaris in paravirt mode is on the way (NetBSD is being updated for Xen3, FreeBSD 7 development branch works, Solaris works with partial functionality).

     Windows (used as a build/test machine)

Should run in an HVM partition.

     MacOS X (used as a build/test machine)

Bzzzt. Due to the restrictions Apple have put in place, it's a little doubtful whether you'll be able to run OS X under Xen - even on Apple hardware - at the moment.

Some notes: Full virt needs hardware support (a VMX or SVM machine). This support is still being optimised (particularly in terms of getting good IO performance) and robustified. You may want to consider this wrt running your services in HVM - certainly you'll want to trial it for a bit to see how well it works for you. You could alternatively (e.g. if you don't like the HVM mode of Xen, or you don't want to buy new hardware) run the unmodified OSes on a separate machine in something like VMware server (the forthcoming Free As In Beer version of GSX).

Provided your hardware supports it, paravirtualisation and full virtualisation work fine together on the same hypervisor. Note also that you can only run 64-bit paravirt guests on a 64-bit Xen, but that you can run 64-bit, 32-bit and 32-bit PAE guests in HVM partitions on a 64-bit Xen (if the hardware supports it!).

Hope that answers your questions.


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