Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!wuarchive!uunet!mcsun!unido!mpirbn!p554mve
From: p554mve@mpirbn.mpifr-bonn.mpg.de (Michael van Elst)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Filesystem Speeds (was Re:  GVP Trade-in)
Keywords: SCSI, GVP
Message-ID: <1159@mpirbn.mpifr-bonn.mpg.de>
Date: 2 Sep 90 20:23:02 GMT
References: <552@DIALix.UUCP> <14069@cbmvax.commodore.com> <558@DIALix.UUCP> <6499@sugar.hackercorp.com>
Reply-To: p554mve@mpirbn.UUCP (Michael van Elst)
Organization: Max-Planck-Institut fuer Radioastronomie, Bonn
Lines: 28

In article <6499@sugar.hackercorp.com> peter@sugar.hackercorp.com (Peter da Silva) writes:
>Last time I saw any benchmarks, the Amiga *with equivalent hardware* was way
>faster than SunOS.

Yes and no. The Amiga "with equivalent hardware" is faster with disk i/o.
It is faster in that sense that it can move data faster into a processes
address space. This is because the Amiga does not use a buffer cache
and therefore does not need the extra copy operation involved in using
a cache. This advantage becomes less when looking at small reads or writes,
the filesystem overhead of the filesystem will make the cache overhead
nearly invisible.
On the other side, the Amiga (the filesystem) is very slow when dealing
with concurrent tasks. The filesystem deals with requests in
first-come-first-served order and concurrent accesses lead to heavy
thrashing of the disk. This is because there is no buffer cache, no
read-ahead and no "elevator"-algorithm. But it is not necessary most
of the time since the Amiga is a single user system and only few users
will put stress on the disk by loading several programs or files at once.
And UNIX, it has to deal with multiple users and a lot of system tasks
requiring disk access therefore it needs these mechanisms to improve
_its_ average demands.

Regards,
-- 
Michael van Elst
UUCP:     universe!local-cluster!milky-way!sol!earth!uunet!unido!mpirbn!p554mve
Internet: p554mve@mpirbn.mpifr-bonn.mpg.de
                                "A potential Snark may lurk in every tree."