we have a performance problem with Xen-virtualized Windows VM`s.
After very good experinces with Windows under Xen and VMDP-drivers, we used the wintertime to update and rebbuild tree SLES-Servers.
The Xen hypervisor 4.1 was so promised, that we wanted to push up our servers for new services comming in 2013.
The old and well running configuration on SLES 10 SP3 and SLES11 was, that we used sparse files for the VM-block devices.
Do we pushed our HP DL360 Servers with more RAM and the RAID with new SAS2 discs in RAID10.
The local storage was now configured with LVM and the images moved with dd into new lvm-volumes.
Everything worked fine. At the end i installed the new vmdp-drivers 2.02 into the vm's and everything looked good.
Next business day the telefones do'nt stoped ringing. The applications (Webserver with seperat SQL-Server) then worked so slowly, that the users couldnt work longer on it. Each SQL-request was worked very quick, but the connection between webserver ans sql-server had a time-gap of up to 10 secons.
So we splitted the servers on to SLES 11SP2 hosts and the user was happy again.
Afterwards we changed the vmdp-driver back to the older version 1.7. The application-performance than was higher, as with 2.02, but never so high, that with SLES10SP3 or SLES11.
We do not understand now, why Xen 4.1 with more RAM, more CPU, more HDD in better configuration as phy-device has so dramatic slower performance.
We see this on different HP DL180 and DL360 Servers.