FAQ Friday

And the answer is here, in these big honkin' 80-millimeter fans. These are Sanyo Denki fans, and these 80-millimeter fans, which are larger than the fans you see in a traditional 1U or 2U server, were in many ways the very first piece of Oxide that we laid down.

This was the cornerstone piece. And when we talked to Sanyo Denki, they were a little surprised to hear that. The first time they came to the office, we were really excited to see them and talk to them because the fans were so important. Why are these fans so important? Why is the geometry of the fans so important?

Well, as it turns out, and I’m a software guy, so I didn’t know this, I learned this as we were building Oxide, that the efficiency of a fan is proportional to the cube of the radius. A big fan moves a lot more air at a lot less power. So it is very important to be able to cool the rack by using these big fans.

But it doesn’t end there. Part of the reason we were excited to see Sanyo Denki is because we wanted to work with them to modify these fans a little bit. As these fans were initially built, at 0% PWM, which is set at their lowest setting, these fans were at 5,000 RPM. 5,000 RPM, we were actually drawing more power than we’d like, and we were overcooling the rack.

We wanted the ability to drop these fans down to 2,000 RPM. Sanyo Denki made that modification for us, which is terrific. Doesn’t mean that they’re always at 2,000 RPM, though. If this CPU starts drawing a bunch more current, which it can, and these CPUs are marvels in terms of their ability to adjust the actual draw with the workload. They get a big workload on there, they’ll draw a bunch more current, and our thermal control loop will kick on. You’ll hear these fans kick up a little bit until that workload has abated, or until we’re down within our thermal margins.

So we are able to air cool the rack because of our integrated hardware software design, very much including these big Sanyo Denki fans.

Thanks, and see you next time.