Re: [Xen-devel] Hacking XenEnterprise / Please Help

[Nate Carlson <natecars@xxxxxxxxxxxxxxx>]

On Fri, 6 Jul 2007, Jim Burnes wrote:
> We need the following features in Xen and we're trying to figure out the 
> best way to acquire them.
> 1. Full virtualization of Windows XP
OK.

> 2. Shared Windows boot image with copy-on-write backing storage after boot.
Interesting. You don't expect a ton of changes to the Windows image, I'm 
guessing?
> 3. Ability to shut down a Windows VM and examine the copy-on-write file store 
> for data written to the drive.
OK.

> 4. High-performance hyper-virtualized Windows drivers
OK.

> Our Problem
>
> The most direct solutions to this problem seems to be:
>
> 1. XenEnterprise with it's hyper-virtualized Windows drivers and using 
> QCOW files for copy-on-write file store.
> Except my experimentation with 3.1.0 last week showed me that there's a 
> bug that prevents blk:tap I/O (which qcow uses) from working correctly 
> with fully virtualized domains. I did see the patch and would be willing 
> to use it against the 3.1.0 source tree except that I don't know if I 
> can even make that drastic of a modification to a XenEnterprise install.
Post on the forum - see if they will fix it for you.

> The other XenEnterprise possibility is to bypass blk:tap and simply use 
> LVM snapshots as copy-on-write images.  This works on RHEL 5, but 
> XenEnterprise didn't have a required kernel feature enabled to allow it. 
> That means I would need to modify the XenEnterprise kernel to enable the 
> feature or go back and hack the version of Xen to allow blk:tap.
Ditto. If you buy XE+support, they would very likely be willing to work 
with you on this.
> In either case, it's a significant modification of a turnkey package.
>
> 2. RHEL 5/Centos 5 with the updated XenSource 3.1.0 RPMs.
>
> I had this running pretty well.  The device mapper in the XenSource 
> 3.1.0 kernel for RHEL 5 allowed LVM snapshot copy-on-writes and I could 
> probably use the blk:tap patch if I didn't mind recompiling the Xen 
> kernel.
> Unfortunately we can't use the hypervirtualized windows drivers unless 
> we're running XenEnterprise.
There are also the SuSE drivers coming available soon. They would let you 
run the open source version of Xen with Paravirt drivers, as I understand 
it.
------------------------------------------------------------------------
| nate carlson | natecars@xxxxxxxxxxxxxxx | http://www.natecarlson.com |
|       depriving some poor village of its idiot since 1981            |
------------------------------------------------------------------------

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