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From: jdp@polstra.com (John Polstra)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Root partition and cylinder 1024
Date: 22 Sep 1995 10:55:47 -0700
Organization: Polstra & Co., Seattle, WA
Lines: 37
Message-ID: <43utb3$d4v@seattle.polstra.com>
NNTP-Posting-Host: seattle.polstra.com
Could somebody help clear up a question about the 1024-cylinder limit
that the BIOS imposes? I can't quite make myself confident of the
answer to this from reading "diskspace.FAQ".
For clarity, I'll use the term "MBR slice" to refer to the regions of
the disk that the BIOS knows about, and "disklabel partition" to refer to
the subdivisions that FreeBSD's disklabel utility manages. I'm using
FreeBSD 2.0.5-RELEASE and SCSI disks.
The question: Does the _entire_ MBR slice containing FreeBSD's root
filesystem need to reside below cylinder 1024 (i.e., begin _and_ end below
that cylinder)?
Or, for example, would this work on a hypothetical 2000-cylinder disk:
MBR slices:
DOS: cylinders 0 - 899
FreeBSD: cylinders 900 - 1999
disklabel partitions:
root: cylinders 900 - 1023
swap, usr, home: cylinders 1024 - 1999
It seems like that ought to work, but I'd like confirmation from
somebody who knows.
For that matter, would it work to have just the first few cylinders of
the FreeBSD MBR slice be below cylinder 1024, with the root disklabel
partition extending beyond that boundary? It seems like, as long as
the FreeBSD bootstrap code is below cylinder 1024, the BIOS should be
able to find it, and the system should boot up OK. Is that correct?
Thanks.
--
John Polstra jdp@polstra.com
Polstra & Co., Inc. Seattle, Washington USA
"Self-knowledge is always bad news." -- John Barth