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ESXi 4 outperforming Esxi 5


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.

V4 physical
vsphere 4v5 physical
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.

I'm stumped?
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2 Solutions
Paul SolovyovskyCommented:
Try reserving the memory for the citrix servers, we've found that it helps execution time since vmware shares memory and citrix needs to spool up quickly depending on load.

What version are your datastores?  With vSphere 5 you should be using updated datastores, if you upgraded from VMFS 3.x versus creating a new datastore then it's running in mixed mode, I would try creating a new VMFS 5 datastore and executing the VM from there.
APNFSSCAuthor Commented:

The esxi v5 hosts were clean builds so the vmfs filesystem should be fine.

None of the guests have reservations on any host. I have added reservations and it hasnt improved the speeds.

Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
I think this is one, for VMware Support!
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APNFSSCAuthor Commented:
yeah I'm thinking so... there isnt a known issue with this that I can find. whats funny is if I run a cpu benchmark utility on both v4 and v5 from within a guest they benchmark close to the same.

We have basic support ... I'm not sure how helpful they will be.
APNFSSCAuthor Commented:
End result on these was a bios setting that was limiting the cpu .... bios setting altered and performance resolved.
APNFSSCAuthor Commented:
Thanks for the holp

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