On Dec 17, 2007, at 1:26 AM, James G. Sack (jim) wrote:
I guess I'm interpreting aol correctly that (xen) full virtualization
just plain doesn't work for Windows guests. That's disappointing --
the
promise was too good to be true, I suppose.
Sorry, I was a little unclear. Assuming version 3.x of Xen and
available VT/AMD-V CPU extensions, Xen's full virtualization, even the
open source version, will work for Windows guests. It just won't work
terribly *well*... that's where the commerical XenServer's drivers
come in to help. Basically, the network and disk drivers that the
standard HVM device model emulates and exposes to Windows are
ridiculously slow. I haven't benchmarked it myself, but I've seen
reports of 25-50% of native performance. Now, for some people who
just need to pop open Excel once a week on their Linux desktop, this
may not matter. But in a server environment where Windows is actually
supposed to do some real work, the additional drivers are almost
required, hence my use of XenServer Enterprise in the writeup.
The situation is also confused a little more by commercial Linux
distributions that include Xen. RedHat is very clear that their Xen
support is only meant for virtualization of other Linux instances.
Windows may run, but don't call them to talk about it.
Oracle's new virtualization solution, also Xen-based, holds a little
more hope. They actually list Windows as a supported OS, but
explicitly state that performance is going to suck. But looking at
their FAQ, there's this interesting sentence: "Oracle is developing
paravirtualized Windows drivers that will substantially improve the
performance of Windows on Oracle VM." And since Oracle's solution is
currently a free download for everyone (you can just choose whether or
not to hand them money for support), the key question is whether or
not those drivers will also be made available for free or if they'll
start hiding them behind the support wall. Time will tell!
As a bonus... if you have a Xen machine with the right CPU and want to
quickly test out Windows support, here's a simple Xen config file that
should get you booted into setup. Just change the paths on the 'disk'
line to point at 1) an empty LVM partition; 2) and your Windows OS
image. You may also have to change the path to the 'hvmloader' and
'qemu-dm' files, as this particular snippet comes from an Ubuntu system.
-----
kernel = "/usr/lib/xen-ioemu-3.1/boot/hvmloader"
builder="hvm"
memory = 512
name = "w2k3-001"
disk = [ 'phy:/dev/Guests/w2k3-001,hda,w', 'file:/images/Windows-2003-
Server-R2-VLA-Disk-1.ISO,hdc:c
drom,r' ]
device_model = "/usr/lib/xen-ioemu-3.1/bin/qemu-dm"
boot="c"
vnc=1
usbdevice='tablet'
vif = [ 'type=ioemu, bridge=xenbr1' ]
-----
Once you 'xen create' that config, connect VNC to localhost port 5900
and you should see the Windows installer! When the install is done,
change 'boot="c"' to "d" and it will boot from the virtual hard drive
into the OS.
--
Joshua Penix http://www.binarytribe.com
Binary Tribe Linux Integration Services & Network Consulting
--
[email protected]
http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
