Virtualization: Kicking and screaming....

by Chris Josephes

I'm working with a product that includes this disclaimer in their support documentation:

"Virtual environments, such as VMWare (and others) are not recommended, and thus not supported."

I can almost see their point. It'd be pretty daunting to gauge a benchmark if a customer described the running host as "1/13th of two dual core processors, 3.1 gigs of memory, and a 27 gigabyte filesystem disk". True, that's a pretty extreme situation, but I wouldn't doubt it if there was the occasional bad provisioning by virtual system installers.

Anyone who implements virtualization is implicitly trusting the VM solution to do the right thing, and when we see the operating system up and running, we just assume everything works perfectly. But let's be honest: almost every VM solution creates some overhead, so you're missing out on a few resources. That loss shouldn't amount to much, but it could mean a lot to an application. And while CPU and memory can be partitioned, device IO such as hard disks are a little sketchy.

To the developers of the above unnamed application, I know it's going to be a big hassle, but five years from now, you're not going to be able to avoid virtualization. Instead of the blanket disclaimers, increase your virtualization knowledge base, and create more test suites. Find out what works, what doesn't, and why. It's still okay to set guidelines on usage, but a wholesale avoidance of virtualization will hurt in the long run.


3 Comments

Stephen Smoogen
2008-04-03 07:29:31
“1/13th of two dual core processors, 3.1 gigs of memory, and a 27 gigabyte filesystem disk”.


How did you know our provisioning scheme? I think too many of us have bought into the appliance thing. We keep plugging in things until a virtual breaker blows. I have seen a 2 CPU system with more than 20 VM's all trying to get their 5% of cpu at 04:00 when the daily cron jobs shoot off.


Is there a Bat book for VM's yet?

Chris Josephes
2008-04-03 08:24:05
"How did you know our provisioning scheme?"


It happens to a lot of people. Hardware runs low, and so people start to over-tune. There's nothing wrong with using every last resource, but sooner or later you'll have to buy another physical machine.


"Is there a Bat book for VM's yet?"


No dedicated virtualization books yet. And if there was one, I wouldn't be the guy qualified to write it.


But, by a strange stroke of luck, it looks like Andrew Kutz just started an ORA blog. He won't disappoint you. And if you ever have the chance to hear this guy speak, don't pass it up.

Chris Josephes
2008-04-03 08:29:02
Oops. Despite showing up in preview, The MT comments application is filtering anchor hyperlinks.


Here's Andrew's blog.


http://www.oreillynet.com/pub/au/3359