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I am having a server running XEN,with ubuntu 12.04 as Domain 0.

Intel VT is turned on by default and i dont want to run any Windows OS as VM. So

1. how can i makesure that all the created VM will be in
paravirtualized mode even with VT enabled?

I have heard that in Full Virtualization hypervisor needs to work hard for emulating all the underlying hardware,which may reduce performance for too much i/o specific applications when compared to para mode.

2.Since i am running only Linux VMs do i really need to enable VT
support?

3.Can i be able to run Linux VM in para mode with VT enabled?

4.Will simply turning on VT support changes virtualization from para to full virtualization??

5.Will there be any performance improvement for VM running Linux OS if VT is enabled?
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3 Answers 3

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1. how can i makesure that all the created VM will be inparavirtualized mode even with VT enabled?

when creating Vm specify whether its in para or full virtmode. For vm to run in para mode it needs special kernel which need to be downloaded from online.So installing from CD may not work.

2.Since i am running only Linux VMs do i really need to enable VT support?

if running vm in para mode there is no need of VT.

3.Can i be able to run Linux VM in para mode with VT enabled?

Yes,Even with VT enabled Linux Vms can be run in para mode.

 4.Will simply turning on VT support changes virtualization from para to full virtualization??

No,it means we can run both para and full vms.We can choose whether to use vm in full mode or in para mode.

5.Will there be any performance improvement for VM running Linux OS if VT is enabled?

If VM is in para mode,enabling VT has no impact on VM.but HVM can be installed only with VT support.

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  1. While creating VMs using virt-install or any virtualization product/tool , you need to specify the type of virtualiztion you want. Ex:- with virt-install -v ensures hvm machine and -p gives you a paravirtualized machine.

  2. With linux also one needs to enable VT support if present.

  3. Yes

  4. Yes. With VT enabled and type of VM chosen the virtualization type changes (obviously in presence of hypervisor).

  5. Yes. This should make a difference.

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5. if we are running vm in para mode,enabling VT support will not make any performance improvement.As its not used in para mode.only HVM needs VT support. –  ananthan Oct 22 '12 at 15:13

If you want to know the basic practical steps for paravirtualization than read this one this will help you to understand what you want http://www.howtoforge.com/paravirtualization-with-xen-on-centos-5.4-x86_64

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But i dont have any issues with installing.Can u please Clarify,whether VM on xen with VT enabled?Will that configuration make vm in Full virtualization,or do i want to disable VT to run vm in paravirtualization mode. –  ananthan Sep 20 '12 at 14:53

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