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From: smb@ulysses.UUCP (Steven Bellovin)
Newsgroups: net.unix-wizards
Subject: Re: Fast Filesystem defaults
Message-ID: <1042@ulysses.UUCP>
Date: Mon, 12-Aug-85 15:34:40 EDT
Article-I.D.: ulysses.1042
Posted: Mon Aug 12 15:34:40 1985
Date-Received: Wed, 14-Aug-85 00:27:27 EDT
References: <597@brl-tgr.ARPA> <1183@umcp-cs.UUCP> <1040@ulysses.UUCP> <1194@umcp-cs.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
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> >On rp07s, it's quite easy to run out of i-nodes; there are *many* blocks per
> >cylinder group, and 2K i-nodes just doesn't make it.  We have to override
> >the cylinder group size on our rp07s just to get enough i-nodes.
> 
> I don't quite understand....  From man 8 newfs:
> 
> 	.B \-i number of bytes per inode
> 	This specifies the density of inodes in the file system.
> 	The default is to create an inode for each 2048 bytes of data space.
> 	If fewer inodes are desired, a larger number should be used;
> 	to create more inodes a smaller number should be given.
> 
> If you have one inode per 2K of data space, then it doesn't matter
> how many blocks/cyl-group; more blocks just means more inodes.  So
> how does having rp07s make any difference?

Sorry, I wasn't explicit enough.  There is a hard limit (MAXIPG) on the number
of inodes per cylinder group; on rp07s, the default cylinder group is so
large that newfs (I believe) *silently* cuts back on the i-node density,
in order to stay within this limit.