I've got a cluster of IIS Servers that we host our web application on. Recently, we converted several of our web servers from physical machines to virtual machines. By converted, I mean we built a template from scratch and cloned it to create the rest of our Web VMs.
The server work, but there is a definite and noticable difference between our VMs and our physical machines. In examining the IIS logs, we found that the time taken to process the request for a certain page we're measuring normally takes about 600 ms to process on a physical server.
On the new VMs, it's closer to 900 ms, which is about 50% slower.
The physical machines are Windows server 2003 R2 Std x86 servers with 4 GB of memory and 2 quad-core 3Ghz processors. Our VMs are quad-processor VMs with 8 GB of RAM running Windows Server 2003 x86 Std R2.
Our first thought was the difference in the processor count, with 8 being in the physical machines vs 4 in the VMs (IIS is a multi-thread-friendly application). To address this, we built a new Windows 2003 Enterprise R2 Server with 8 vCPUs and put in in the mix. This new server runs with lower CPU utilization, but the page render time is still the same.
Our cluster is new and is not being heavily utilized. CPU contention is not an issue. I've even tested by moving one of the web server VMs to it's own host for a day and saw no change. Our web server admin insists none of these measures have changed anything.
Are there any other settings or options I should look into tweaking to improve this deficiency? My guess is he's seeing expected overhead from CPU virtualization, but everything I'm reading says we should not see this big of a performance hit.
Thanks!