Wrong Kind Of Cluster, Pal

My phone rings. Today I hate my phone.

“Hi Bob. I’d like to talk about clustering if you have a minute,” says the guy on the other end.

“Sure thing. What do you want to know?” I reply.

“A customer of mine wants to use VMware to build a ROCKS cluster.”

“In what way? For testing?”

“No, production. They want to install it on virtual machines running in a VMware cluster.”

…a few seconds pass…

“You’re joking, right?” He’s got to be joking, I tell myself.

“Why? I thought you liked VMware.”

“VMware helps you drive utilization of your servers up, operating on the principle that most of your servers are sitting there doing nothing. That isn’t a true about a computational cluster. You build a computational cluster to solve hard problems, ones that need a lot of CPU to get an answer. If you install ROCKS in a bunch of VMs the cluster will only have as much CPU as you have physically, minus the overhead of VMware. It doesn’t buy you anything.”

“What about Virtual SMP?”

“Virtual SMP doesn’t magically create new CPUs, just let’s a VM use additional real CPUs. What you want is a whole bunch of fast, non-virtual machines with real SMP.” What’s the saying? Buy the bullet, rent the gun?

“With VMware on them, right on.”

“No, dude, with the ROCKS cluster software on them.”

“So how do I virtualize this cluster?”

“You don’t, man. You don’t.”