Recently I had to add a second external hard drive to the web server here to get a clone of the main drive to work with on another machine. The web server is a Mac Mini, with data cloned nightly to an external 2.5" hard drive via FireWire. I plugged in another 2.5" drive, after hooking up an old FireWire hub, and got the clone started, then promptly forgot about it. A day or so later I remembered, did another clone to catch any updates, and went to unplug the drive, and about burned my hand the enclosure was so hot. It was at this point that I realized that my original drive was no longer online, after some testing it appeared that the heat had caused it to shut down. Not good! So the search was on to find a way to keep the drives cool, should I ever need to stack them again in the future.
After some searching, I found a number of fans that connected via USB, a perfect way to add a small fan to get some air moving around the drives. One model stuck out because of the name, Thermaltake, well known for their cooling products. So I headed down to the local comp-u-mart, and picked up the Thermaltake Mobile Fan II
Before hooking it up, I thought it best to take a few temperature readings. Ambient Temp was 79.3F, Drive Enclosure 1 Temp read 109.0F, with the second drive having been disconnected the night before. I fired up the second drive, and watched the enclosure temp climb past 118F within just a few minutes, and this was simply with the drives powered up and spinning, no drive activity to speak of. Now, I knew that the drive enclosures had little airflow through them, but the aluminum cases had ventilation holes front and rear, and this apparently was simply for aesthetics, any cooling provided is certainly minimal. Time to fire up the fan!
The Mobile Fan II plugs in via USB, using an included retractable cable, keeping cable clutter to a minimum. The fan end of the cable uses a custom connector for fan power, which the fan then plugs into. It would have been nice if the fan itself had a standard USB jack, allowing for a standard USB cable to be used, but the retractable cable seems relatively sturdy and should not present any issues.
I set the fan to its lowest speed setting using the built in knob, according to the spec sheet this should have been about 1300 RPM, which, again according to the specs, should have a noise level of 17 dBA. Unless I had my ear right against the fan, I couldn't hear a bit of noise coming from it over the whirring of the drives. I placed the fan, still on low, next to the drives, and saw the temperature drop rapidly from the 122F that it had reached, dropping down to 114F in under a minute, and under 100F after a few more.
At the highest setting, the fan is capable of moving 47.28 cubic feet per minute of air, which is quite a lot for such a small fan, obviously the lower speeds will move much less.
There are a number of novelty fans that plug into the USB ports on the computer for keeping the user 'cool', but having seen these in action, their gentle breeze wasn't all that appealing for serious cooling, and I knew the Thermaltake brand wouldn't disappoint, and it didn't.
It is a great fan for notebooks, which aren't known for having large fans, or can be used anywhere you have a USB port and need some air moving, external drives are a great place for such a fan, if you have drives that don't include fans in their enclosures. Larger 3.5" drives especially would be great candidates for a fan like this.
I paid $14 for mine locally, a quick Google has these anywhere from $8 - $22 at a number of retailers.