Green computing

[bluesmoon]

We had a green computing BoF at openhackday yesterday. There were a whole bunch of ideas that popped up, but for the most part we were discussing ways to measure the power consumption by machines so that we could tell what code changes resulted in lower power utilisation, and consequently, a smaller carbon footprint

Comments

[thaths]

You don't need to know how much power your application uses. You just need to reduce CPU utilisation in a way that will let you use fewer boxes. n boxes will always take up more power than n-1 boxes.

True, that. But, given 'n' boxes, how will you decide whether to run service A or service B?

[bluesmoon]

Run the one that can run on n-1 boxes :)

[say_yes04]

I say run it on your desktops, that way all the servers can be switched off!

/me [g,d&r]

[nvivek]

Use VMware :-)

[bluesmoon]

how would that reduce CPU load if you're already maxing out on CPU?

[nvivek]

It won't. If your algorithm is cpu-intensive, then nothing can help you other than a different algorithm.

My comment referred to:
he hit us with this amazing insight. You don't need to know how much power your application uses. You just need to reduce CPU utilisation in a way that will let you use fewer boxes. n boxes will always take up more power than n-1 boxes.

When you virtualize, you end up using n-1 boxes for n machines. Which is what the amazing insight says. Reducing cpu utilization for power-savings is not something an application should be concerned about. It's something that the OS should do. Currently the OS doesn't do a very good job of it. Hence, the easiest way to use less CPUs is to fool several OSes into thinking that they have an exclusive CPU to themselves, while actually using one.

PG&E actually offers a discount on your power bill, if you virtualize your data centre. And this is old news (http://weblog.