CPU of virtualized Exchange Server ?

[eagleh]

I have had my Exchange server P2V'ed to an ESX Cluster (2 hosts with 16 processors in total). Since the previous physical Exchange server had 2 CPUs, so this virtual one has 2 vCPU accordingly. Everything works fine, no complain. However, from what I have read, it seems it may get a better performance if I put it back to 1 vCPU, comments? any risk?

Many thanks,

EH

[khughes · Accepted solution]

Our physical exchange had 2 cpus as well. When we virtualized it my boss didn't want to mess with anything on the p2v. So we still have 2 vCPUs which barely take a hit, and more ram that it will ever use but thats still the mentality of the people above me

Understanding how ESX uses the CPUs, unless the application is built for utilizing multiple cpus, like a citrix box, you're going to tend to get better performance out of a 1 vCPU VM. Basically instead of waiting for 2 cores to open up, your VM would only need a single core to open up making commands flow through much faster. In theory 1 vCPU should be able to do the trick but if you're like me (with people above you that wont let you touch the box) it doesn't hurt to leave it at 2 vCPUs

• Kyle

[vmPUNK]

on one side of the coin exchange can leverage multiple cpus so its good to have them

on the other if you have a lot of 1vcpu vms on the same esx it will be harder for the 2vcpu vm to get its cycles, so i would start worrying about this box if you had 10 other vms with 1vcpu

if you dont have much utilization in exchange, you can easily take it back to 1vcpu and keep your vi uniform where all vms have only 1 vcpu - the change shouldnt cause you any issues

[eagleh]

Thanks Kyle. Just wondering if anybody could convince me how better the performance could be improved by doing so. worth it or not?

[khughes]

There are quite a few threads about Exchange VMs and virtualizing the Exchange

http://communities.vmware.com/message/814032#814032

There is one that has a couple good links, if you just search community for "exchange" you will get quite a few hits for past threads. All have a lot of info in them but almost everyone goes back to the 2 linkes that are listed in the thread i posted above.

- Kyle

[ejward]

Check "CPU Ready" in performance monitor in VC. If it's high, it means that the VM is ready to process threads but can't get a free CPU. What's high you ask? You've really got to comapare it to other VMs. If it is high on a 2 CPU VM, it might be because it can't find 2 fee CPUs at the same time. If it's really low, it's not having an issue and you won't benifit by giving it just a single CPU.