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From: brad@griffin.itc.gu.edu.au (Brad Rosser)
Newsgroups: comp.unix.xenix.sco
Subject: Why the frequent disk access in Xenix?
Summary: Disk Access
Keywords: Xenix, disk access
Message-ID: <1991Mar17.001408.16603@griffin.itc.gu.edu.au>
Date: 17 Mar 91 00:14:08 GMT
Sender: Bradley Rosser
Reply-To: brad@griffin.itc.gu.edu.au (Brad Rosser)
Followup-To: comp.unix.xenix.sco
Distribution: comp
Organization: Griffith University, Brisbane, Australia
Lines: 40

Why do simple shell scripts access my hard drive so much?

I have Xenix 2.3.2 running on a 24Mhz '386 AT with a 40Mb MFM drive and 8Mb of 
memory.  I've got 2Mb for a /tmp ramdisk, and it boots with a self-configured 
878 i/o buffers.

When/if I run DOS with a 1Mb disk cache (say), a simple "show time" batch 
file:

		:loop
		<show_time>
		<sleep for 60 seconds>
		goto loop

wouldn't access the hard disk after the first pass, where everything off the
disk would be placed into the cache.

Yet the equivalent shell script on xenix

		while true
		do
			clear
			date | <awk script> | banner
			sleep 60
		done

causes that disk access light to flash every minute.  Indeed, if I just type
the command

		sleep 1

at the keyboard, it causes a "disk flash" every time!

I would've thought the text/program of /bin/sleep would be cached, the inode
be in memory, etc.

What does Xenix do which accesses the disk for each (shell) command?

Bradley Rosser
brad@griffin.itc.gu.edu.au