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From: judah@whuxcc.UUCP (Judah Greenblatt)
Newsgroups: net.unix-wizards
Subject: Re: Disk/Tape Request Size Questions
Message-ID: <244@whuxcc.UUCP>
Date: Fri, 15-Aug-86 19:39:14 EDT
Article-I.D.: whuxcc.244
Posted: Fri Aug 15 19:39:14 1986
Date-Received: Sun, 17-Aug-86 07:26:53 EDT
References: <146@sheba.UUCP>
Distribution: net
Organization: Bell Comm. Rsrch., Morristown, NJ
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> What limits exist on the size of single transfers
> to/from disk and tape (tape block size) in the Unix
> world, and elsewhere.

The maximum tape block size for Unix machines I have used:
AT&T 3B20	6K max,  5632 byte recommended
Pyramid 98x 	30K max
CCI Power 6/32	32K max, 16K recommended

> What effects on performance are there for using larger
> size transfers (i.e. do other requests pay a penalty
> while a large transfer is being serviced)?

On the CCI, transfers of over 16K bytes at 6250 BPI disable interrupts
overly long, causing the system to loose clock interrupts.
-- 
Judah Greenblatt		"Backward into the Future!"
Bell Communications Research	uucp: {bellcore,infopro,ihnp4}!whuxcc!judah
Morristown, New Jersey, USA	arpa: whuxcc!judah@mouton.com
  * Opinions expressed are my own, and not those of the management.