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From: jc@odin.ucsd.edu (John Cornelius)
Newsgroups: comp.periphs
Subject: Re: Hard drive speeds
Message-ID: <6992@sdcsvax.UCSD.Edu>
Date: 29 Aug 89 15:59:37 GMT
References: <17640@ut-emx.UUCP> <16567@pasteur.Berkeley.EDU> <6987@sdcsvax.UCSD.Edu> <1989Aug28.050055.28526@utzoo.uucp> <13700@brunix.UUCP> <1989Aug29.040250.23754@utzoo.uucp>
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Reply-To: jc%andataco.uucp@ucsd.edu (John Cornelius)
Organization: University of California, San Diego
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In article <1989Aug29.040250.23754@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>In article <13700@brunix.UUCP> sgf@cfm.brown.edu (Sam Fulcomer) writes:
>>>Somebody's been reading old papers... Very few modern Unixes swap.  Paging
>>
>>In the modern Unixes which I know about processes are born with a swap. Other
>>swapping (during normal scheduling) depends on the implementation of the
>>scheduler, but they (as far as I know) all do it. 
>
>"What we have here is a failure to communicate." :-)
>
>The "swapping" that many modern Unixes do has little or nothing to do with

Well, yes!  I have read the old papers, among others.

I did not mean to start a religious war on the net.  As Henry points out,
the nature of swapping in systems with BSD ancestors is not really swapping.
On the other hand, while that should be all of the Unices in existence it
is not.  The purpose of the comment was to point out the misplaced emphasis
on transfer rate when evaluating disks and I stand by the comment.

In the past 4 years we've seen average seek times drop from around 28ms to
around 14ms and transfer rates increase from 2Mbps to 3Mbps.  Rotational
speeds, however, have remained at about 3600RPM giving a rotational
latency of about 8ms.  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. 

John Cornelius
Andataco
aka jc%andataco.uucp@ucsd.edu