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From: filbo@gorn.santa-cruz.ca.us (Bela Lubkin)
Newsgroups: comp.periphs
Subject: Re: Hard drive speeds
Message-ID: <19.filbo@gorn.santa-cruz.ca.us>
Date: 2 Sep 89 16:19:50 GMT
References: <17640@ut-emx.UUCP> <3170009@hprnd.HP.COM>
Organization: R Pentomino
Lines: 29
X-Claimer: I >am< R Pentomino!

In article <3170009@hprnd.HP.COM> Kurt Chan writes:
>> As seek times approach rotational latency the speed
>> with which the data may be accessed will be dominated by rotational
>> latency and controller behavior, not by seek times. 
>
>Disk manufacturers have come up with solutions to this exact problem.  Some HP
>drives now spin at 4000 RPM, while Hitachi and Imprimis have drives which rev
>up to 4800 and 5400 RPM, respectively!

Why not build a second set of heads radially opposite the first?  This halves
latency instantly (doubles RPM, if you wish); alternatively, it lets you play
adaptive seeking games where the two sets of heads are stationed over different
cylinders, etc.  This can be extended to N sets of heads, N probably < 8 (you
start running out of room...)  Another idea is to put multiple heads on a
single arm on each platter, so that while head 5A is over track 50, 5B is over
track 600 (e.g.).  This can halve your maximum seek distance (which doesn't
halve your maximum seek >time<, but does lower it).

I know heads are expensive.  A drive built with some of these ideas would be
damn expensive, but damn fast, too.  >Someone< would be willing to pay for it...

(One of these years nanotechnology will happen.  We'll buy memory by the MOLE;
no moving parts).  >Bela<

>Kurt.

Bela Lubkin     * *   filbo@gorn.santa-cruz.ca.us   CIS: 73047,1112
     @        * *     ...ucbvax!ucscc!gorn!filbo    ^^^  REALLY slow [months]
R Pentomino     *     Filbo @ Pyrzqxgl (408) 476-4633 & XBBS (408) 476-4945