This is the latest (and, I hope, final) post about my hard drive heat problems. (All in a 2G iMac G5, 20″ – the last one without a built-in iSight camera.)

By a fortuitous coincidence my friends at Deltatronic offered me a 400GB Samsung HD400LJ SATA drive at a reasonable price, and I bought it. Reviews on this drive indicated that it was quieter and ran a little cooler than my previous Seagate drive, at the expense of being slower in some situations; well worth it for me.

After mounting it, I saw that the new drive has no convenient smooth surface on its face to mount the temperature sensor, so I took advantage of the cable length (which I had increased in the previous installment) and tacked the sensor onto the part opposite from the connectors, just for testing. It turns out that this is also conveniently out of the fan’s airstream, so chances were this would be the hottest part of the drive.

And indeed, after 10 days of testing the temperature sensor tracks consistently 4-5C higher than the internal SMART temperature – remember that, with the standard sensor mounting, this was the other way around. As a result, the drives were usually hovering right near their upper limit of 60C; not a desirable situation. With the new placement the SMART temperature oscillates between 48 and 52C, still not ideal but much better. The tradeoff is increased fan noise, which I don’t mind much – although I must be one of the few iMac G5 owners who doesn’t. I was hoping the new iMacs, which have a larger fan directly below the drive, would run lower temperatures, but from what people say, they decided to lower fan speeds at the expense of maintaining the 58C operating point.

The Google paper (pdf) about drive reliability did conclude that temperatures weren’t a significant factor, but the majority of their drives ran in the 25-40C range, with almost none over 50C. Their graph does show that failures begin to rise when you get over 45C, so I prefer to err on the side of caution here. I couldn’t find a single working fan control program for the iMac G5 but there seem to be several for the Intel iMacs – I’ll certainly get one when I upgrade, perhaps next year.

Currently, I have a G3 iBook/600MHz which can run any Mac OS X between 10.0 and 10.4; a PowerBook G4/1GHz; the iMac G5/2GHz, which is my main working machine; and a Core Solo Mac mini with 512MB. I only lack a Core 2 Duo machine to have all CPU platforms of the last 10 years for compatibility testing. (Justifying all these Macs to my wife is, as yet, an unsolved problem…)

Since I now have two left-over SATA drives without a convenient external case to use them in (not to speak of several older PATA/IDE drives), I also bought a Cables Unlimited USB-2110 drive adapter. This is a small cable header which plugs into both 3.5″ and 2.5″ IDE drives and also (over two extra short cables) into SATA drives, with an external power supply. Works quite well and I now can switch among my old drives for backups, and easily test others that come in.

After Leopard comes out with Time Machine in a few months we’ll probably see a boom in external RAID or NAS drive cases, and then I’ll have a place to put the two SATA drives. None of the solutions currently on the market quite fill my requirements. Ideally I’d like a drive case that has USB2, FireWire and gigabit Internet interfaces and with space for at least 3, ideally 4, internal SATA drives…