What is bps/cpg?

Ion-Mihai Tetcu itetcu at apropo.ro
Mon May 3 11:41:21 PDT 2004

On Fri, 30 Apr 2004 14:07:00 -0400
"Kevin A. Pieckiel" <pieckiel+freebsd-questions at sdf.lonestar.org> wrote:

> I was reading the man page for bsdlabel, specifically looking for what the
> bps/cpg value for a new filesystem should be.  The man page states:
> bps/cpg
>              For 4.2BSD file systems, the number of cylinders in a cylinder
>              group.  For LFS file systems, the segment shift value.  Defaults
>              to 16 for partitions smaller than 1GB, 64 for partitions 1GB or
>              larger.
> Okay.  Sure.  That leaves a few questions:
> 1. What is the purpose of cylinder groups?
> 2. What are "reasonable" values for this parameter?
> 3. Why, if the default is 16 or 64, did sysinstall create my various
>    filesystems (on various machines) with values of 8, 28552, or 32776?
> I'm just trying to understand why this value is set to these numbers by
> sysinstall, and to what I should set this value when I add a HDD to a
> computer.

Try reading the comments in /usr/src/sys/ufs/* beginning with
/usr/src/sys/ufs/ffs/fs.h. Do it with a piece of paper and a pencil at
hand ;-)

Unregistered ;) FreeBSD "user"

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