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From: Terje Mathisen <terje.mathisen@tmsw.no>
Newsgroups: comp.arch
Subject: Re: ancient OS history, ARM is sort of channeling the IBM 360
Date: Tue, 25 Jun 2024 08:49:43 +0200
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John Levine wrote:
> According to Lawrence D'Oliveiro  <ldo@nz.invalid>:
>> How much of theoretical disk bandwidth was the filesystem capable of
>> using? Because I know early Unix systems were pretty terrible in that
>> regard, until Berkeley=C3=A2=E2=82=AC=E2=84=A2s =C3=A2=E2=82=AC=C5=93F=
ast File System=C3=A2=E2=82=AC=C2=9D came along.
>=20
> My recollection is that if you were using QSAM with multiple buffers
> and full track records it wasn't hard to keep the disk going at full
> speed. Later versions of OS do chained scheduling if you have enough
> buffers, doing several disk operations with one cnannel program.

Even on (MS)DOS it was easy to saturate the hard drive from a single=20
program, you just needed large enough (i.e. at least a full track each)=20
buffers.

I did end up making special file/record layouts which were optimized for =

this, using exactly 4kB for each header+bitmap record.

Terje

--=20
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"