**How** harmful is a hard disk spin cycle

hard drivelifespanstatistics

It is conventional wisdom┬╣ that each time you spin a hard disk down and back up, you shave some time off its life expectancy.

The topic has been discussed before:

Common explanations for why spindowns and spinups are harmful are that they induce more stress on the mechanical parts than ordinary running, and that they cause heat variations that are harmful to the device mechanics.

Is there any data showing quantitatively how bad a spin cycle is? That is, how much life expectancy does a spin cycle cost? Or, more practically, if I know that I'm not going to need a disk for X seconds, how large should X be to warrant spinning down?

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But conventional wisdom has been wrong before; for example, it is commonly held that hard disks should be kept as cool as possible, but the one published study on the topic shows that cooler drives actually fail more. This study is no help here since all the disks surveyed were powered on 24/7.

Best Answer

I am not aware of any studies on the subject, but I do know what the SMART data tells me:

For one particular drive (a WD Scorpio Blue 2.5") a start-stop count of ~200,000 or a load-cycle count of ~600,000 corresponds to SMART value 0 (i.e. the disk is at the end of its life according to SMART). (This is a laptop drive, they are made to handle a larger number of spindowns than desktop drives are.)

As these values come from the manufacturer, I assume they represent the manufacturer's best guesstimate for what their drives can handle. Lacking independent data, I'd be inclined to think that the manufacturer's guess is probably better than mine, so you could probably do worse than using those numbers in calculating the X.