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Subject: Disk spin down and cache usage

Disk spin down and cache usage

From: Jürgen Hestermann <juergen.hestermann_at_gmx.de>
Date: 2004-12-15

>>> a big cache is wasted since it's emptied
>>> every time we spin down the disk.
>> Do all drives do this when spinning down?
> I think so, since the purpose of spinning down
> is to save power. However it is not defined in
> the ATA specification, so theoretically different
> drives could differ in this aspect.

If not fixed in a specification manufaturers could
choose to implement different levels of power saving:
1.) Just switch off motor but keep running everything else
2.) Switch off everything
Or even better, the ATA specification could be extended
in this direction.

>> If the cache could be saved it would prevent spin up for quite a long time
>> and therefore save batterie drain. I think that disk manufacturers should
>> have considered this kind of usage (especially for disks used in mobile
>> environments).
> 2.5" disks are made for laptops, which generally don't spin
> down the disk until the computer is effectively idle. Therefore
> spending battery power on keeping the cache alive would likely
> have little real-world advantages.

It would have advantages in all cases where devices read or write slowly
but constantly from/to disk. This kind of devices will propably appear
more often in the future for all kinds of data recording and replaying (not only
mp3 but other measuring tasks or even video).

Jürgen Hestermann.

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Received on Wed Dec 15 18:01:28 2004


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