xen on xen

[angeloalfa]

Hello,
I have the necessity for an university plan to create two virtualizzation levels, on the first one I must create some Xen virtual machine, between these to create a cluster xen and to second level creating one or more virtual machine. The problem is that I do not succeed to create, in the first level, more of a virtual machine in HVM mode.
I use debian lenny on all the levels.
You would give a hand to me?

[falko]

To be honest I don't know if it's possible to create a VM inside a VM. I've never tried this.

[angeloalfa]

yes, it's possible, in HVM mode. But second vm in hvm mode not working.

[syadnom]

XEN can not run XEN, meaning that you cannot run a VM host inside another VM.

KVM CAN do this. you can run 5 servers inside KVM on one box, then inside those 5 VMS you can run 5 more servers under KVM.

25 servers on one box might seem excessive, but that and more is possible.

Also, KVM in RH5.4 or Centos5.4 is a bit faster overall than Xen, though Xen gives faster access to devices so network and I/O will be a bit faster in Xen. KVM can pass PCI devices to virtual machines, like network cards or storage devices like SATA controllers which would make the VM have NATIVE speeds off those devices.