Over the last few weeks/months I’ve noticed something on our VMware Infrastructure cluster. All of the servers that we converted from physical to virtual servers use up much more CPU and total memory than equivalently taxed pure virtual machines doing the same tasks.
I have 2 examples:
Our old file server runs Windows 2000 Advanced Server. It is a file server for profiles and user home drives, for staff only. It is probably the biggest offender of CPU alerts in Virtual Center out of 14 virtual machines. As a comparison, I have a new pure virtual machine that runs Windows Server 2003 R2 Enterprise that also acts as a file server. It hums along using single digit CPU usage all of the time. It has far more active connections and bandwidth usage during the day than the old server. I really can’t explain it. If I remote into the old server and look at the task manager, there’s no process using a lot of CPU or anything out of the ordinary.
We also have an old domain controller/print server/dns/wins/Cisco ACS agent server that runs the same way, but a little less severely. I have removed all but its Print and ACS Agent roles, and it still goes ‘red’ due to CPU usage a few times a day. All students are printing to a new Windows Server 2003 R2 print server, and it feels much faster. I’ve even started using it myself instead of the old server.
After the P2V process, I removed all software not necessary to the server’s task. It could be just garbage on the servers that I can’t see making them more resource hungry. In my opinion P2V only started the task of allowing us to consolidate and decommission servers that were going to become a liability, without going through the pain of migrating data and services. The migration will still need to happen, but it will let us migrate at a time when we will able to give it the attention it will require.
One thing that people should be aware of, in case they already aren’t, a very simple and sometimes overlooked thing during a P2V process is to make sure that any specific hardware vendor software, drivers, etc. are removed or uninstalled once migrated over to a virtual machine. I’ve had the case a few times where I left something from the hardware vendor, and although it didn’t fail on boot, I noticed that it would creep up on me over time and either blue screen me after months of being up, or would cause a higher than normal CPU or RAM issue. Just an FYI. Great articles, very useful.
[...] I have been trying to ‘fix’ the issues I had discussed in the original posting about our servers which had undergone with Physical to Virtual migration. [...]
That sounds interesting but not very objective to come to any conclusions.
Someone would need to do a benchmark of a new setup VM against a P2V one.
It would also be interesting to know if there is a difference from what physical machine it has been virtualized. Maybe that could help pinpoint a possible cause. Of course in such a test both setups should run the exact same OS, patches and applications.