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From: jerry@oliveb.UUCP (Jerry F Aguirre)
Newsgroups: comp.bugs.4bsd
Subject: default number of inodes limited on eagle or other "dense" drive
Message-ID: <4775@oliveb.UUCP>
Date: Tue, 8-Sep-87 15:03:26 EDT
Article-I.D.: oliveb.4775
Posted: Tue Sep  8 15:03:26 1987
Date-Received: Wed, 9-Sep-87 06:31:26 EDT
Organization: Olivetti ATC; Cupertino, Ca
Lines: 34
Keywords: newfs mkfs eagle inode MAXIPG

Index:	etc/newfs.c 4.3BSD

Description:
	The newfs(8) command claims to create by default 1 inode for
	every 2048 bytes of data.  If the drive has a large number of
	sectors/cylinder (like the Fujitsu eagle 2351 or 2361) then the
	actual number of inodes is less than that.

	This is because in <sys/fs.h> the constant "MAXIPG" limits the
	maximum number of inodes/group to 2048.  With the default 16
	cylinders/group an eagle has 48x20x16=15360 sectors in a
	cylinder group.  In practice this works out to 3700 bytes per
	inode.  On a 2361 eagle it is 64x20x16=20480 sectors/group
	resulting in 4800 bytes per inode.

	Specifying a smaller bytes/inode to newfs or mkfs will not alter
	the result as the "MAXIPG" is a hard limit on the resulting
	value.

Repeat-By:
	If you don't trust the above calculations then do a newfs on an
	eagle or other drive with more than ~600 sectors/cylinder.
	Then calculate the number of bytes/inodes.

Fix:
	Temporarily use the -c options to specify a smaller cylinder
	group size.  For an eagle 8 is OK.

	A more permanent fix would be to have newfs calculate the default
	cylinder group size based on the number of sectors/cylinder, the
	specified bytes/inode, and the "MAXIPG" value.

	Newfs (or mkfs) should generate a warning message if the user
	specifies a cylinder grouping that limits the bytes/inode value.