Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!xstor!iverson
From: iverson@xstor.com (Tim Iverson)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: Disk seek optimisation
Message-ID: <1991Jun07.171325.2963@xstor.com>
Date: 7 Jun 91 17:13:25 GMT
References: <1991Jun5.111750.951@csc.canterbury.ac.nz> <1991Jun07.024728.29844@xstor.com>
Reply-To: iverson@xstor.com
Organization: Storage Dimensions, Inc.
Lines: 14

In article <1991Jun07.024728.29844@xstor.com> iverson@xstor.com (Tim Iverson) writes:
>you can improve by leaps and bounds over FIFO by using an algorythm that
>reduces seek distances and/or latency time - latency is very hard
>(impossible?) to reduce by scheduling and remain efficient.

Argghh.  I forgot about SCSI's modify data pointer: 0 latency by telling
the host adapter what block is coming (perhaps different from the initially
requested block) and then transferring the block under the head *now*.

Above, I was referring to reducing latency via head scheduling - certainly
possible, but probably prohibitively expensive in terms of calculation time.

- Tim Iverson
  iverson@xstor.com -/- uunet!xstor!iverson