Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!jerry
From: jerry@olivey.ATC.Olivetti.Com (Jerry Aguirre)
Newsgroups: news.software.b
Subject: Re: tuning number of inodes for cnews
Message-ID: <50435@olivea.atc.olivetti.com>
Date: 8 Mar 91 06:45:30 GMT
References: <1991Mar1.230651.4574@NPIRS.Purdue.EDU> <1991Mar3.001647.18652@zoo.toronto.edu>
Sender: news@olivea.atc.olivetti.com
Organization: Olivetti ATC; Cupertino, CA
Lines: 24

In article <1991Mar3.001647.18652@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes:
>we don't have much real experience with the matter.  Utzoo, which keeps most
>news four days, has about 90MB of news using about 40K inodes.

I run 398MB and 141K inodes, about the same ratio.  In general 1
inode per 2K bytes should be about right.

The problem is that sometimes you don't get as many inodes allocated as
you expect, even less than the default value.  There are a number of
limitations.  SYSV file systems limit one to 65K inodes max per file
system.  4.[23]BSD systems have an internal hidden limit on the number
of inodes per cylinder group.  If you have a drive with lots of sectors
per cylinder (most modern winchester drives) then the resulting number
of inodes will be much less than what is advertized as the default.  And
mkfs doesn't inform you of this little detail.

One can sometimes work around the 4.2BSD limitation by using -C 8 to
reduce the size of the cylinder group.  Some system don't like this and
refuse to cooperate.  It is possible to lie about the geometry in
/etc/disktab and achieve the same effect.  Drives with odd numbers of
surfaces and sectors can be particularly troublesome.

The important thing is to verify the ratio after you make the file
system.  Don't just trust that it did what you asked.