Yes you can.
>First off, can you run a 2cpu license on a 4 socket server (with only 2 >cpus installed)
Is there a software upgrade from 2 to 4 cpu license for ESX
Well you should ask your reseller ...... I am not keen to licensing barin storms...
Can I add 2 cpus to an ESX box without reinstalling ESX
Yes. Sit it down. Plug the new CPU's. Start it again. Insert the new 4-way CPU. Voila'.
I just did this on a couple of boxes and piece of cake
ESX looks at home many CPUs are installed, not empty sockets, so you should be fine for licensing.
After you put in the CPUs you will have to enter a new 4 CPU license, unless of course you have upgraded to VI3 and have the central licensing server running, then you will just add a 2 CPU license to the pool.
The only problem with this plan is that the vendors charge a huge amount of $$$ for the additional CPUs and that price docent come down a year latter. So in terms of value for what you are paying you lose out because a year from now the same amount of money will buy better/faster CPUs, but from a licensing standpoint there are no issues.
I agree, I say we just buy all 4 now, but my boss doesn't think we can spend any more than the 2 CPU box costs until next fiscal year.
Thanks for your help!
As others have said, ESX will just recognise it. I did this last week on a server.
One thought, if you're planning to add CPUs, you probably planning to add more VMs too. If you're going to add more VMs, are you going to add more RAM too?
If you're planning to add more VMs/CPUs/RAM at a later stage, you may want to increase the Console Os's memory from the default of 192mb. If you're going to do this, you'll need to increase the disk space allocated to the Console's swap file. Therefore, you should size the partition it goes on accordingly from the outset. I suggest sizing this at 1600mb from the start, which is twice the max 800mb assignable to the Console OS.
With a year lag in between, you might end up with mixed steppings. Mixed steppings might work, or it might not. Something for further research.
you can lookup the HP Product Bulletin (google for product bulletin) which can be downloaded from the HP site.
here you can search the newest processor models for proliant servers. Be aware of the fact that processors should have the same stepping level etc...