Testing (continued):
During the normal use of the enclosure over the first few days I noticed two things; that the fan was not loud but it was audible, and that the top surface of the enclosure got pretty warm. Placing my hand next to the exhaust fan revealed that not much air was being moved, even though it sounded like there might be! I was skeptical about the efficiency of the fan's design and positioning from the beginning, and now it seemed like the issues I feared were coming true.
I decided to take a very close look at the thermal profile of each drive to see how they fared under idle and load conditions. A thermal probe was affixed to the center of the top of each drive, and they were monitored under a variety of conditions. The idle condition was established by powering up the drives with no activity for a period of at least one hour. The load condition was established by looping the long benchmark from HD Tach RW 3.0.4.0 several times while also copying a few thousand MP3s to and from the drives. I first powered them up without the housing; just the drives fastened to the drive tray in order to get power and a USB connection. Once data was recorded like this, the drives were allowed to cool off and they were then tested inside the sealed enclosure.
The chart above shows exactly why the housing feels warm; the drives are not being adequately cooled inside the enclosure! I have never had drives get this hot no matter where they were installed, and over 50C is just too hot for my liking! You may also note that once installed into the housing the idle and load temperatures really aren't that different. The drives get hot and stay hot. Two hours after running the load test, the drives had only cooled by a couple degrees, while they should be expected to drop back down to idle temperatures in open air or a moderately well ventilated enclosure.
One thing is clear, I will not continue to use this enclosure as is. It is too loud to use on my desk or with my HTPC, and I will not risk the health of my drives due to the high temperatures. I just haven't figured out if it is worth the effort to modify the rear panel to add a different fan. If it was actually a 60mm fan as advertised it would be an easy fix of swapping out the fan and maybe adding some more ventilation holes up front, but a unit that measures 44mm is a different story.
