Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!mailrus!tut.cis.ohio-state.edu!ut-sally!utah-cs!utah-gr!uplherc!sp7040!obie!wsccs!terry
From: terry@wsccs.UUCP (terry)
Newsgroups: comp.sys.amiga
Subject: Re: AmigaDos don't thrash no more!
Message-ID: <208@wsccs.UUCP>
Date: 27 Feb 88 03:28:15 GMT
References: <8504@sunybcs.UUCP>
Lines: 51
Summary: huh?

In article <8504@sunybcs.UUCP>, ugpete@sunybcs (Peter Theobald) writes:
> AmigaDos should sort disk requests by track. This way if three processes
> ask for three different files scattered all over the disk, instead of
> jumping around like a Tasmianian Devil getting blocks from first one
> file, then the other then back to the first, AmigaDos would load in the
> blocks on the tracks currently nearest the read head.

	Good idea.  That way if the head is in position 0 and someone requests
block 1 and someone else requests block 5 an someone requests block 79, I can
wait forever for it to get to 79.

	Example:

[cli-1] copy df0: df1: all

[cli-2] run program-that-opens-ralph-the-file-begining-on-df0:-track-79

	While I agree that the seek optimization algorythm needs work, it
doesn't need that.  A better method (if you had ram) would be to cache the
sectors on either edge (some reasonable number) and then spend most of your
time flitting around in the center.  A floating cache, perhaps the 10 most
frequently accessed tracks, as determined by a track access count table with
timer entries to preserve 'freshness', could also be used.  Writes could be
flushed when absolutely necessary or when the head went over a track on it's
way to another track that wasn't in cache.  This would solve the biggest
problem (writes) that occurs with FaccII.  Unfortunately, to impliment any
nifty-save-me-time algorythm, you have to make mountable disks unmountable
or at least "forced-flushable" with a user command such as 'sync' under UNIX.
Unfortunately, most modern computers can't tell when you are reaching for
the drive door to remove a disk, yet :-).

	Agreed, however, that something SHOULD be done.  I hate the ST
people telling me 'my drives faster than yours'... with their new format
toys, an ST can do 800+ K on a disk too, and it's still fast.  My Leading
edge at work is faster, and it's *OLD*.

	DO SOMETHING COMMODORE!


PS: I would write one myself, but I'm afraid that since Commodore doesn't
    advertise in the US except inside magazines dedicated to the machines
    that the reader already has, I wouldn't be able to sell enough to make
    it worth my while... A placed-ly high source in MicroSoft says that's
    why they're not porting Xenix to it, and the ST is too low end.


| Terry Lambert           UUCP: ...!decvax!utah-cs!century!terry              |
| @ Century Software       or : ...utah-cs!uplherc!sp7040!obie!wsccs!terry    |
| SLC, Utah                                                                   |
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