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Date: Mon, 22 Aug 2005 19:47:07 -0700
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To: Borja Marcos <borjamar@sarenet.es>
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Cc: freebsd-hackers@freebsd.org,
	=?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@freebsd.org>
Subject: Re: IBM Active Protection System Approach
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Borja Marcos wrote:
>> I think this will need to be tailored to the exact type of "mishap"  
>> one wants to protect against.
> 
> 
>     I think that the main purpose of the shock detection system is  to 
> allow data to be recovered from the disk in case the laptop is  broken. 
> By parking the heads asap you can avoid damaging the plates  with the head.
> 
>     At least that's what I read. The disk won't be necessary usable  
> after being dropped, but at least the plates should be readable.

no,
the aim is to detect the LACK of acceleration as the laptop goes into freefall.
You have about 1/4 a second to get the heads in once you detect that you are falling.

Quick by human standards but an eon in computer terms.

> 
>     In that case, priority number one would be a fast parking of the  
> head. However, it could lead to a worst-case data loss with  softupdates 
> and the disk cache, isn't it?
> 
> 
> 
> 
>     Borja.
> 
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