Monday, July 18, 2005

Rack cooling

I just spent some time trying to improve the air-flow around and through our blade-rack. In the process I learned that our vent-tile lifter has wandered away somewhere along the line. I think I managed to improve things a touch.

Our datacenter's air-flow is a little hap-hazard, but our cooling capacity is far enough ahead of heat generation that we don't have hot-spots yet. The blade-rack is by far the #1 heat producer in the room. The SAN disk-packs do not pump out the heat you'd think they would with the power they suck, all that energy gets converted to actual work spinning disks rather than being resisted off in the process of number-crunching. The rise in temp from front to back for the blade rack has to be pushing 25 degrees F.

I moved a couple of vent tiles to right in front of the blade-rack, and that helped some. Then some air-flow testing (thanks to a couple of hairs around 4" in length, they make good free flow testers) inside the rack itself showed that we're getting a bit of back-to-front circulation over the top of the topmost blade chassis. That's not good. Opening the rack door caused the circulation to maintain front-to-back up there, so that told me the front door needed attention. We found another fully perforated front door and replaced it. The circulation went a bit neutral, but at least it wasn't back-to-front like before.

All in all, the work reduced the temp of the back of the rack to 'only' about +15 to +20 degrees. I don't have a thermometer I can use for this, so I'm not certain. But it is a bit cooler back there now.

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