Comment 3 for bug 550409

 1. create the guests
The first set of guests I created (both Windows and Linux) were created with virt-manager. I used default settings for both Windows and Linux guests. Windows guests defaulted to IDE emulation, and Linux guests defaulted to Virtio emulation. I have since tried all possible emulation modes on both guest OS's.
Without virt-manager, I have created Linux guests using vmbuilder.
vmbuilder kvm ubuntu --suite lucid --flavour virtual --arch i386 --libvirt qemu:///system --user=foo --pass=bar

 2. start the guests
Guests are normally started with virt-manager, which results in the following command:
/usr/bin/kvm -S -M pc-0.12 -cpu qemu32 -enable-kvm -m 512 -smp 1 -name winxp -uuid eb0416e2-54d2-d4cb-936d-331edbe443c0 -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/winxp.monitor,server,nowait -monitor chardev:monitor -localtime -boot c -drive file=/datahauz/storage/software/Windows/EN_WINDOWS_XP_PRO_WITH_SP2.ISO,if=ide,media=cdrom,index=2 -drive file=/datahauz/storage/kvm/tinyxp.img,if=ide,index=0,boot=on,format=raw -net nic,macaddr=52:54:00:0d:11:23,vlan=0,name=nic.0 -net tap,fd=37,vlan=0,name=tap.0 -chardev pty,id=serial0 -serial chardev:serial0 -parallel none -usb -usbdevice tablet -vnc 127.0.0.1:0 -k en-us -vga cirrus

 3. run the benchmarks
Several benchmarks were used. Under windows I used IOmeter, and also timed file copies while observing both host and guest disc access. I did the following file copy tests.
1. Scp a 2GB file from the hosts disc, to the guests disc.
2. Scp a 2GB file from the hosts memory to the guests disc.
3. Scp a 2GB file from the guests disc to the hosts disc.
4. Scp a 2GB file from the guests disc to the hosts memory.
Then I put the guest disc image in /dev/shm and tried the same tests again.
With the guest disc hosted on /dev/shm, I get slightly better disc speeds (15MBps windows, 30MBps Linux)

Another point to note, is that when scping to the Linux guest disc, I get about 20MBps, but to the guest memory (/dev/shm) I get 38MBps. Either way, Linux guests do better on both disc and memory throughput, but are still much slower (1/4) The speed I would expect.
My expectations are based on performance results under VMware, Virtualbox, and Xen, which are all quite similar (~40-70MBps disc throughput)