Number of cpus and hardware migration

[PhallusaurusRex]

2 questions:

I saw this tutorial on how to clone vms from by just copying it in the data store browser and re-adding it to the inventory.

Is this kosher? can it cause any problems? Its a freebsd 9 AMD64 bit installation.

Also, is it safe to move a VM like this from an hp desktop with a core2duo onto a hp dl360 xeon?

And finally, both these machines are quad cores; should i set the number of virtual processors in vsphere to 4 or leave it at 1?

[a2alpha]

Rather than copy the entire machine, just copy the .vmdk disk to a new folder and then create a custom virtual machine in the vi client and select use an existing disk. I find this works well and you know the .vmx config files are ok and not pointing to some other machine. If you have a vCenter server can you not just storage vMotion?

When you boot the guest machine up it will see the new CPU type and should install any drivers necessary. I haven't done this with freebsd, just windows and red hat machines.

As for setting the number of vCPUs. Set the virtual machines to use only what they need. Just because the host has 4 cores you don't need to make your guests have 4. Incidently this could actually lower performance of the guests due to scheduling methods.

Hope this helps,

Dan

[PhallusaurusRex]

thanks for the quick reply dan

the setup im going for is 1 production freebsd for web, 1 identical for development, and 1 sandbox for trying stuff. The production one is the one that needs to perform here. Should i go with 1 cpu on all of them, or 2 for production and 1 for sandbox and 1 for dev?

Also, can changing the number of cpu's have adverse effects if performed after a guest os has been installed on a 4 cpu setting?

[a2alpha · Accepted solution]

You'll need to look at what resources they each need, certainly if the production needs the processing power of 2 vCPUs then giving it 2 and splitting the remaining two between the dev and sandbox would probably be best. In our environments if pre implementation capacity planning isn't possible we would start with 1 vCPU per machine and increase if necessary.

The majority of virtual machines I have worked on have been fine when scaled up and down with the number of CPUs, but as I said, it is mainly windows and red hat. This post talks about the situation for Windows Server 2003 but I would imagine there will be similarities. http://communities.vmware.com/thread/29415

I think you really need to test it though, with a view to maybe building a single vCPU system. Moving from a 4 to a 2 vCPU should be fine as they will still be using a multiprocessor driver.

Hope this helps!