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Path: utzoo!watmath!clyde!bonnie!akgua!gatech!ut-sally!seismo!rlgvax!hadron!jsdy
From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: net.unix-wizards
Subject: Re: partition sizes in 4BSD systems
Message-ID: <123@hadron.UUCP>
Date: Fri, 6-Dec-85 11:13:09 EST
Article-I.D.: hadron.123
Posted: Fri Dec  6 11:13:09 1985
Date-Received: Sun, 8-Dec-85 03:28:26 EST
References: <46@brl-tgr.ARPA> <100@hadron.UUCP> <317@l5.uucp>
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Organization: Hadron, Inc., Fairfax, VA
Lines: 43
Keywords: partitions, root, swap
Summary: Gorey details on 4.2 partition sizes.

In article <317@l5.uucp> gnu@l5.uucp (John Gilmore) writes:
>In article <100@hadron.UUCP>, jsdy@hadron.UUCP (Joseph S. D. Yao) writes:
>> For BSD, the root partition is always 15884 sectors ... This is nice
>> and reasonable for an RP0[456].  ...  Partition B, often used
>> as swap, is 33440 sectors long.
>Hmm, I always wondered where those numbers came from.  ...

From /etc/disktab:
rp06|RP06|DEC RP06:\
	:ty=removable:ns#22:nt#19:nc#815:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#340670:\
	...
	:ph#291346:bh#4096:fh#1024: (actually, no longer true)
				    (because they drop 3 tracks)
				    (for bad block information.)
19 sectors/track, 418 sectors/cylinder.
 38 * 418 = 15884
 80 * 418 = 33440
697 * 418 = 291346
===
815

Oddly enough,

rm03|RM03|DEC RM03:\
	:ty=removable:ns#32:nt#5:nc#823:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#131680:\
32 sectors/track, 160 sectors/cylinder.
 209 * 160 = 33440

rm05|RM05|DEC RM05:\
	:ty=removable:ns#32:nt#19:nc#823:\
	:pa#15884:ba#8192:fa#1024:\
	:pb#33440:pc#500384:\
32 sectors/track, 608 sectors/cylinder.
 55 * 608 = 33440

But nothing else fits.	;-)
-- 

	Joe Yao		hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}