Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!oliveb!amiga!boing!dale
From: dale@boing.UUCP (Dale Luck)
Newsgroups: comp.sys.amiga
Subject: Re: simple AmigaDos thrashing solution
Message-ID: <108@boing.UUCP>
Date: 24 Feb 88 05:26:15 GMT
References: <8504@sunybcs.UUCP> <1177@goanna.oz> <107@boing.UUCP> <5282@well.UUCP>
Reply-To: dale@boing.UUCP (Dale Luck)
Organization: Boing, Milpitas, Ca.
Lines: 30

In article <5282@well.UUCP> ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) writes:
>In article <107@boing.UUCP> dale@boing.UUCP (Dale Luck) writes:
>>The trackdisk driver as originally written did have more than 1 track
>>buffer. We had to limit it to 1 though to keep all those 265k
>>systems working.  Maybe it is time to rethink this strategy and let it
>>loose again.  [ ... ]
>	Personally, I'm a believer in functional seperation.  IMHO, the
>trackdisk.device should not be trying to second-guess the guy making
>requests of it.  Its sole responsibility should be to get them bits off the
>media and into memory.  It should also know how to move the head around so
>it can find them bits.

However it is the trackdisk device that decided to treat the floppy disk
as something you can only read and write a track at a time instead of a
sector at a time like most other mass storage devices. So forcing the
file system to know about the peculiarities of the device is forcing
the file system to be more intelligent then maybe we should make it.

The same kind of problem occurs with scsi devices. Scsi was invented so
that a filesystem of some nature could deal with logical sectors, a whole
bunch of them. However the to get the max performance from a complete
system it helps to inform the file system that your hard disk is
split up into 4 heads 900 cylinders and 17 sectors per track. Instead of
some other configuration.

If we can speed up this mess by appropriate buffering in the
trackdisk device then other file layout strategies may be able to take
advantage of this level of buffering as well. Kind of like magic.

Dale Luck
Boing