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From: dupuy@douglass.columbia.edu (Alexander Dupuy)
Newsgroups: comp.unix.wizards
Subject: mkfs/newfs: not enough inodes (SunOS 4.0)
Summary: "cylinder groups must have a multiple of 16 cylinders"
Message-ID: <5794@columbia.edu>
Date: 2 Aug 88 15:42:31 GMT
Sender: news@columbia.edu
Reply-To: dupuy@douglass.columbia.edu (Alexander Dupuy)
Organization: Columbia University Computer Science Dept.
Lines: 26

We're bringing up a Sun-4 fileserver, which will take over much of the news and
mail duties here.  We have two 898M Hitachi drives, with those biiiig cylinders
(1005 sectors ~= 500K each).  I wanted to create a nice little 50M filesystem
with lots of inodes for news.  This doesn't seem to be possible.

The most inodes/cylinder group which mkfs or newfs allows is 2048.  With the
default 16 cylinders/group, this works out to 1 inode / 4K, which is a bit low
for news.  I went and pulled the old Sun-Spots issue off the archive server to
see what the workaround was.  The solution which someone came up with then was
to use 8 cylinders/group - fairly obvious in retrospect.  Unfortunately, under
SunOS 4.0, mkfs/newfs say:

	"cylinder groups must have a multiple of 16 cylinders"

which does not warm my heart.  On a Sun-3 running SunOS 3.5, the minimum seems
to be 4 cylinders/group.  Is there a reason for this?  What would happen if I
compile my old 3.5 mkfs source under 4.0 and build an 8 cyl/grp filesystem
anyhow?  I suspect the kernel will panic and die at some point, and don't care
to find out the hard way.

So, does anyone out there have any useful suggestions?

@alex

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