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From: jw@sics.se (Johan Widen)
Newsgroups: comp.unix.questions
Subject: QIC-11, QIC-24 and dump(8) tape length
Message-ID: <1469@sics.se>
Date: Fri, 7-Aug-87 18:55:51 EDT
Article-I.D.: sics.1469
Posted: Fri Aug  7 18:55:51 1987
Date-Received: Sun, 9-Aug-87 13:31:22 EDT
Reply-To: jw@sics.se (Johan Widen)
Distribution: world
Organization: Swedish Institute of Computer Science, Kista
Lines: 27

What are the good and bad points of the QIC-11 and QIC-24 tape formats?
We have a Sun which supports both formats and I would like to know if one
of these formats is better in some sense.

I would also like to know how to calculate dump(8) tape length for a say
9 track cartidge tape. I do not have the source for Sun dump but I suspect
that dump regards all tapes as 8 track (8 data plus parity). My guess is also
that 9 track cartridge tape is used by writing 8 data bits and 1 parity bit.
Is this the case?

The formula I am using right now for calculating tape size is as follows:
	I use the tape size written on the cassette with no safety margin!
	density = 10000   (thats ten thousand)
	size = 450 feet

My guess is that one of the following formulas is correct:
	(tape size)*((9 tracks)/(8 tracks))*(safety factor)

	(tape size)*(safety factor)

where (safety factor) is something like 0.9 or 0.94 (depending on who
you talk to).
-- 
Johan Widen
SICS, PO Box 1263, S-163 13 SPANGA, SWEDEN
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