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10.3: Use Secure Empty Trash to reclaim hard disk space
Authored by: johnsawyercjs on Mar 13, '05 04:41:56AM

If you could KEEP a hard drive spun down for a significant amount of time (a half-hour or longer, to allow it to cool down) when it's not being accessed, that might increase the life of the drive, but if you have only one drive in your Mac, that drive is constantly being accessed while you're using the Mac, so a spindown setting would be pretty useless in that situation since the drive would constantly be spun down and up again, and this might add to the wear and tear caused by a hard drive's main enemy, heat. The Energy Saver prefpane's setting "Put the hard disks to sleep when possible" doesn't let you set how much user inactivity time after which the drive is supposed to spin down, so who knows what figure it uses? If it spins down after only a few minutes of user inactivity, many Macs will spin their drives down and up over and over, as the user pauses or steps away from their Mac for a few minutes throughout the day. I think some third-party utilities let you set the delay before a drive spins down; but if the drive isn't able to stay spun down for more than a half-hour or so at a time, a spindown setting would probably be useless or worse since it wouldn't have time to cool down substantially.

When a hard drive isn't suffering extra wear and tear by being spun down and up constantly, the primary thing that ages a drive is heat, which the drive generates plenty of, due to the friction of its spinning, and makes it more susceptible to the heat generated by the processor chip, which can generate more heat than the hard drive (especially the G5 processor)--the rest of the circuitry in the Mac doesn't tend to generate nearly as much heat. Heat wreaks havoc with everything in the drive--the read/write heads, the drive's controller board, etc. Manufacturers put a heat sink and fan on the computer's processor chip, and some also provide a fan blowing air over the hard drive (some of Apple's designs do), but it might be useful to put a fan right on top of the hard drive (actually about a half-inch above it for clearance/airflow).

You'd think a Mac with more than one drive, in which you're not conciously accessing the secondary drive, would be a candidate for spindown control on the secondary drive, but one problem with the Mac OS (and others?) is that it often looks at volumes that you don't access, when you decide to access another volume, so that if you (or the OS) access a file on one drive, and you have one or more other hard drive mechanisms connected to your Mac that have spun down, OS X will often spin up all attached drives. I don't know why, but it usually makes useless any spindown control settings, unless you're in the habit of often not using your Mac for stretches of a half-hour or longer. Only sleep mode will spin down a hard drive and keep it spun down until you decide to access it (usually). So, with this unfortunate spindown override, having a spindown setting active might actually wear out a drive faster, since it won't be given enough time in a spun-down state to cool off substantially. A drive that's always spinning will probably induce less wear on its bearings, than one that's always spinning down and up again--in fact, these days, a drive that's always spinning will almost always suffer the failure of any other part before its bearing fails.

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