Spin down HDD after disk sync or before power off

[Warren Block]

On Thu, 4 Feb 2010, Erich Dollansky wrote:

> let me do.
>
> On 04 February 2010 am 04:44:04 Warren Block wrote:
>> On Wed, 3 Feb 2010, Oliver Fromme wrote:
>>
>>> Alexander Best wrote:
>>> No -- *Please* make sure that the disks are only spun down
>>> upon an actual power-off command (i.e. when reboot() is
>>
>> Could you elaborate a little on why that's bad?  It seems like it would
>> be similar to a standby/resume action.
>>
> every disk has a limited number of restarts before it dies.

Okay.  For future reference, here are the numbers I've seen:

power cycles (Seagate): 50,000 lifetime

    normal head load/unload (Hitachi): 600,000 lifetime
emergency head load/unload (Hitachi):  20,000 lifetime

> In case of a reboot, it is already known when the command is given that the machine will restart without being powered of.
>
> If you spin-down the disk, you lose one start cycle.
>
> It is not that important but if it can be done with just one if, please, just do it.

AFAICT ad_shutdown can't tell whether it's called for a reboot or a 
poweroff, it's just told to "shut down".  So maybe it's one if, but it's 
somewhere above ata-disk.c but below reboot(RB_POWEROFF).

-Warren Block * Rapid City, South Dakota USA