RE: [Xen-users] Production Xen Deployment (Windows Guests)

["Sanket Agrawal" <sanket.agrawal@xxxxxxxxxx>]

Greg,

 

This question was answered just this morning (in response to my question). You need virtualization capabilities in the processor (Xeon has VT technology) unless you get MS to share Windows source code with you to modify OS for Xen virtualization. AMD is going to release pacifica for Opterons in July (tentative).

 

More details below on Xen from Javier Guerrra's email:

 

historically, virtualization systems (VMWare, QEmu, VirtualPC, etc) on x86 had to use heavy emulation techniques to compensate for the lack of real hardware virtualization.

Xen uses a different tradeoff, it relies on modifications to the guest OS. it doesn't need any new processor feature, and doesn't use it if present.

of course, as we all know, that doesn't work with closed source OSs, so the Xen people began to work on a real virtualization feature. The tradeoff chosen was to make it depend on the new hardware features so it wouldn't get much worse overhead than the already working paravirtualization.

In short:

without Pacifica/VT:

- paravirtualized guests (linux, bsd, solaris): very low overhead

- unmodified guests: can't run.

with Pacifica/VT:

- paravirtualized guests (linux, bsd, solaris): very low overhead (same as

before)

- unmodified guests: run with somewhat bigger overhead; but not so bad as old software-only solutions.

or, another way to see it:

modifiable OS: can run paravirtualized, very low overhead. doesn't need nor use any new virtualization feature of the processor.

non-modifiable OS: need Pacifica/VT processors, get higher overhead on disk and graphics.

there are some plans about using some new CPU features even on paravirtualized

domains to get lower cross-domain switching times, or easier PCI

administration, or to mix 64bit/PAE/32bit guests.... but all those are in the

future.

 

---

From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Greg Freemyer
Sent: Wednesday, May 24, 2006 1:24 PM
To: Alex Pearson
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Production Xen Deployment (Windows Guests)

On 5/24/06, Alex Pearson <alex.pearson@xxxxxxxxxxxxxxxxx> wrote:

Hi All,
    Appologies in advance i know this topic comes up a lot, but i
couldn't find answers to these specific questions.
    I've been looking through the list and couldn't really find any
explicit examples of people deploying Windows Server Guests in
production Xen environment.  Have many people done this?  Is xen stable
enough to do this?   Has windows proved stable when running on xen....
What hardware    are people using (we normally buy HP servers).
    If it proves practical we would hopefully use iscsi and our NetApp
filer for the storage too.  Any comments or examples of setups?
    Any responses are very much appreciated, in an effort to redeem
myself for asking such a commonly covered question i'm happy to add my
finding to the wiki to help other find the info easier ;-)  I didn't
turn anything up searching the mailing list.
    I guess what i'm really looking for is someone to say "i've tried
this, and this works great! ;-)" (with an example of what 'this' is!)

Thanks in advance!

Alex

If you don't know, for Xen to work with a 
Windows Guest it requires VT support in the hardware/bios (Intel hardware only, 
AMD is not shipping its equivalent silicon yet).

I've seen a several 
people posting on this list about the above including some benchmarks, but I 
don't know if any of them are in production. 

Resources I've found to 
better know what has VT support:
http://wiki.xensource.com/xenwiki/IntelVT
http://www.intel.com/products/processor_number/proc_info_table.pdf

Note: 
Maybe people here that have working systems could update the wiki site 
above.

Also if your looking for a vendor that will support your xen setup 
I copied this from another list:
>>
A really neat vendor to add to 
your list is Virtual Iron 

One aspect of their approach to VT is to treat 
each node on an
infiniband network as a NUMA node in a single image scale up 
approach.

It is public info that Intel Capital is investing there.
http://www.eweek.com/article2/0,1895,1863527,00.asp
<<

Greg
-- 
Greg Freemyer
The Norcross Group 
Forensics for the 21st Century 

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