I'm a little stumped. I've to two hosts one is vsphere 5 enterprise plus and the other is vsphere 4 advanced.
I use these hosts to run a citrix workload. The other day I noticed that the execution time of a cpu intensive task on the version 5 host was taking 2 times longer to run that on the verison 4 hosts.
After some testing I can see that the application is hitting a single core and that the amount of time to process the same transaction between servers is 2:20 on v4 and 4:20 on v5.
I've ruled out the build of the citrix server by migrating one from v4 to v5 and the longer result occures.
So the only differences I can see is that the citrix servers have hardware version 7 on the v4 host and version 8 on the v5 server.
I'm 99% sure it's a cpu thing, it makes no difference if there are other users on the system during testing the results are the same as with no users on the system.
The application is running some basic type scripts which is looping and processing some data in memory and I notice that the memory for the process increases by about 100mb during the processing... it's just that the v4 server does this cpu intensive task much faster than v5...
And yes I have checked everything the network/config of guests the lot.