hard disk power down

[Andy Green]

Thorsten Leemhuis wrote:

> On 14.05.2007 12:53, Richard Hughes wrote:
>> On Mon, 2007-05-14 at 10:37 +0100, Jonathan Underwood wrote:
>>> There's another factor here though, as I understand it hard drive
>>> lifetime is largely determined by the spin up/spin down frequency. So
>>> while it may save a bit of power spinning down more often, this might
>>> significantly shorten drive lifetimes. I'd definately want to have an
>>> option to disable that, if my understanding is correct.
>> Correct, hence why we only want to spin down the drive after a few
>> hours, rather than minutes or seconds.
> 
> Laptop drives are designed for lots of power spinning cycles (lots more
> than server drivers for example). So spinning hard disks in laptops down
> after 15 or 20 minutes should be totally fine afaics. Even after a
> shorter timeframe (5 minutes) might be fine. But doing the same on the
> server might destroy you hard disk quickly.

You can get some numbers on it: random 3.5" desktop drive specifies a
lifetime of 50,000 "start/stops"

http://www.hitachigst.com/tech/techlib.nsf/techdocs/C5C895A725AC713E862571D5004E4EDB/$file/Deskstar_E7K500_DS.pdf

Random 2.5" drive specifies a lifetime of 300,000 "load/unload cycles":

http://www.hitachigst.com/tech/techlib.nsf/techdocs/D9DA661AA5D3E44B86256CEC0075C7B2/$file/Travelstar5K80-Datasheet.pdf

The 3.5 drive quotes a "low duty cycle" MTBF of 114 years ;-) but I
don't think the flash holding the firmware will last that long.

If in reality you expected the drive to last 5 years and it was in use
half that time, spreading the budget of 300,000 starts and stops over
that period looks like you can afford to do something like 6 an hour...
vs one an hour for the 3.5" drive...

-Andy