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I have to admit, the whole hard drive cooler concept seems a little flawed for home users. Sure, the 36GB RAID arrays at work needs cooling, because they've each got 5x 9.1GB Ultra-Fast-Wide-N-Funky drives in them, spinning away at 10,000RPM, stacked into a mid-tower-sized box and pretty much constantly in use (Lotus Notes is a killer for disk activity). On a cold evening in the computer room (or pretty much any time in the computer room, actually) you can warm your hands in the jets of hot air blasting out of the drive cabinets. However, as much as I'd like to, I don't have one of those arrays at home. I don't even know of anyone who does. If anyone wants to send me one for long-term review, I will change this article to reflect that :).

Basically, HDD's consist of the Head-Disk Assembly (HDA) area (a sealed enclosure usually filled with extremely clean, dry, low-pressure air) and a printed-circuit board (PCB) populated with controller electronics along the bottom of the drive. Both of these are sensitive to heat. The electronics will suffer errors or stop working if overheated, the same as any electronic component such as a CPU. The HDA enclosure contains moving parts that are calibrated with extremely fine tolerances. Thermal stress will make the metals expand and the tolerances change. In fact, for a long time hard drives have been designed to recalibrate the heads against the platter as the entire assembly expands due to heat. If the thermal expansion is too high or too sudden, the drive may come out of alignment causing data errors, or even be physically damaged.

In a decent sized case, you can usually get enough air whizzing around so that the drives keep cool. In a full-tower my favourite trick is to mount the drive above the power supply (long cable required) with an exhaust fan behind it, so any heat it produces is immediately blown out the back of the case. In a mid-tower, presuming you don't have too many devices, you can usually get away with a case-front fan (a good idea anyway) and putting the drive in the bottom bay. However, if you've got a fast, warm drive (say, a 7200rpm unit) and you slide it neatly into the only free internal bay of your minitower case (with other drives on either side), you could possibly heat the drive to the point of damaging itself in the long term.

It is presumably for this purpose that the first unit in this review was designed.

The Just Cooler HD-600 (AUD$30.00 from www.pccoolers.com) is a slimline fan mounted in a vented sleeve which attaches to the bottom of the drive and pulls air across the electronics, venting into the case. Presumably it's designed to be nice and slim so as to minimise the interference with the bay below the drive. However, as pretty much all modern hard drives entirely fill a 3.5" bay, it's going to interfere with the lower bay anyway. In fact, in the 2 cases I tested it in (AOpen HX-08 Fulltower and a generic mid-tower) the internal 3.5" HDD bays have fold-in fins to hold the drive in place while you screw it in. That's useful, and fairly common. However, there are standards for these kinds of things - when you increase the drive side height by 1mm or so (by adding this cooler) it will no longer fit into the bay. This is a pretty severe flaw which, in my case, forced me to use the unit in a 5.25" bay, which required using a separate drive conversion kit (spacer rails, pretty common, but obviously not supplied with this cooler). I note that the Macase K10 does not have these fins and therefore you could use this unit in a 3.5" bay in that case - keep in mind it will need the bay below the drive to be empty. Futher, there were no screws supplied with my unit. Apparently there normally are - but they will need to be tiny button-head screws otherwise they will extend past the edge of the drive and make it too wide to mount. I had trouble finding small enough screws with the correct pitch (even in my big jar of screws, collected over years of building PC's). If they are normally provided with the unit I guess this is not a problem.

As mentioned earlier, the unit blows air across the bottom of the drive and back into the case. Where does this air come from? Err.. inside the case. Also, I wonder if the unit might suck in it's own exhaust near the drive IDE connector. It seems that the air could get into an ever-warmer cycle around the drive. If you have decent case cooling then this will be less of a problem.. but in that case you probably wouldn't need this unit. I tried mounting the unit further towards the IDE connector, but due to the screw-hole alignment the plate then extended a fair bit out beyond the IDE connector, which makes it extremely tricky to get the cable in there and continue it onto the next device.

For this unit I measured the temperature at the top of the drive because the bottom, where all the actual cooling is occurring, has lots of air blowing around now which would affect the temperature readings. If the unit is doing it's job the top of the HDA enclosure should be cooler. I have a little Tandy dual-source temperature guage with a remote probe. It was tested in the full-tower, on a Quantum Fireball +KA 13.6GB in a 5.25" bay in a mounting kit, with a CD-ROM above and another hdd below. I tested with and without the unit for 30 mins of drive defragmentation with all case covers on. The result? No difference in temperature. None at all. This is in a case with fairly decent airflow through the motherboard area, so you would expect the hot air from the exhaust to be sucked away in that stream and ejected from the case. Yes, the electronics on the bottom of the drive were probably cooler, but overall there was basically no difference. I could fill a paragraph with theories behind why this is.. but I think it basically boils down to the Just Cooler HD-600 being junk. Troublesome to mount and doesn't perform.