[ltp] Does hdaps [APS] work on non-Thinkpad hard drives?

[Henrique de Moraes Holschuh]

On Sat, 05 May 2007, r8scq7b02@sneakemail.com wrote:
> My understanding of APS [Active Protection System] on supprting Thinkpad
> laptops is that the mechanism detects movement and when it reaches a
> critical level, the APS, via software, parks the drive heads.

Correct.  Other manufacturers are now offering the same, but IBM beat them
to market by at least one year on ThinkPads.

> However, according to the ThinkWiki problem page [1], there are problems
> with non-Thinkpad branded hard drives. To quote: Additionally, the
> following ATA commands are implemented by ThinkPad-branded drives but are
> not supported by most other laptop drives: UNLOAD IMMEDIATE (needed for
> the Active Protection System) SECURITY FEATURE SET (needed for disk
> password protection)

Unload Immediate is not a common feature on disks yet.  And most HD
techsheets are really pathetic, so you will have to, e.g. limit yourself to
Hitachi disks, and get their full tech spec sheet in their technical
library.  It describes *all* HD commands, so you find out right away what it
supports or not.

Besides, if you are going to use it, you also want the disk to survive at
least 300K unloads...  I really recommend hitachis for this, as they survive
600K unloads.

> Is this correct? How can other hard drives not be supported by APS if all
> it does is park the heads, which every hard drive can do?

Unload immediate *unloads* the heads, which is not parking.  It *lifts*
them off the platter and secures the head assembly so that they cannot hit
the platters even under a big-G shock.

Not all HDs "parks" head by unloading.  And even those which do won't unload
them FAST (without a cache flush), which unload immediate does...

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh