Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!oliveb!intelca!mipos3!td2cad!cpocd2!howard
From: howard@cpocd2.UUCP (Howard A. Landman)
Newsgroups: comp.sys.mac
Subject: Re: A/UX disk I/O (real numbers)
Message-ID: <1154@cpocd2.UUCP>
Date: 1 Mar 88 17:20:29 GMT
References: <8802251936.AA23485@cory.Berkeley.EDU> <7215@agate.BERKELEY.EDU> <5314@spool.cs.wisc.edu>
Reply-To: howard@cpocd2.UUCP (Howard A. Landman)
Organization: Intel Corp. ASIC Systems Organization, Chandler AZ
Lines: 21

In article <5314@spool.cs.wisc.edu> planting@speedy.cs.wisc.edu (W. Harry Plantinga) writes:
>Let me see if I have this straight.  The mac II hardware (without DMA)
>is capable of reading data off the hard disk at 512Kb/sec, compared to
>the sun 3/50 (with DMA), which reads data at 240Kb/sec?

This is apples and oranges (Apples and Sun-sets?) because the 512KB/s was
"best case", i.e. "an unfragmented 8+ Megabyte file", while the Sun number
is "typical", i.e. a benchmark designed to be representative of the
typical state of a real system.  Also the Mac was running Mac OS, not UNIX,
and the file might have been in the top-level of the disk, thus avoiding
any HFS overhead.  Without more info the number is intriguing but
inconclusive.

Also, buffer size *can* have an immense impact on performance, but it
always has an effect on memory usage as well.  Imagine 20 files open
with a 32KB buffer for each - that's 640KB just for file buffers.  Not a
big problem in an 8 MB machine, but on a 1MB or 2MB machine?

-- 
	Howard A. Landman
	{oliveb,hplabs}!intelca!mipos3!cpocd2!howard
	howard%cpocd2.intel.com@RELAY.CS.NET