Altering Virtual CPUs on a Hyper-V VM

[nathan]

I have a running Virtual Machine on a server 2008 r2 host. It only has 1 virtual processor, if i were to stop this and add another would there be any ramifications to the virtual machine? Edited May 9, 2014 by nathan

[localzuk]

Shouldn't be any negative effects, no. I do it all the time, adjusting machines when they have new needs etc...

[nathan]

I should just note that i meant to put 2008 r2 and not 2012 r2. I presume it's the same?

[tmcd35]

Depends on the OS and software you are running. If it needs it and the OS supports SMP then it'll have and use 2 CPU's. So long has the host can support the configuration (enough resources) - then you'll probably get a bit more speed for the VM.

[nathan]

The VM is running server 2012 r2 and running a service that uses SQL Server so i presume adding another virtual processor would help.

[sonofsanta]

It'll be fine.

 

And if it some how, some way, goes horribly wrong, you can stop the machine again and revert to a single CPU, or restore from a snapshot. But in all honesty, you'll be fine.

[nathan]

Cool, thanks guys.

[Norphy]

Adding CPUs won't do any harm. If you're going from one to multiple CPUs, the OS may change the HAL but that's painless these days.

 

If you're reducing the amount of CPUs that you're allocating, you may need to be a little more careful. Most software won't care but if you're running the likes of SQL Server on your VM, you need to take a bit more care.