Date: Mon, 23 Aug 1999 13:35:04 -0600 From: "Justin T. Gibbs" <gibbs@caspian.plutotech.com> To: Bruce Evans <bde@zeta.org.au> Cc: imp@village.org, phk@critter.freebsd.dk, cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: Re: cvs commit: src/sbin/i386/fdisk fdisk.8 fdisk.c Message-ID: <199908231935.NAA09623@caspian.plutotech.com> In-Reply-To: Your message of "Tue, 24 Aug 1999 04:45:21 %2B1000." <199908231845.EAA01679@godzilla.zeta.org.au>
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>>Last time I tried to do this, I ran into the problem that I could not >>find out the disks' geometry. At least what the BIOS thought the >>geometry was so that it would acutally create a bootable disk. >>FreeBSD lies for at least the UltraStor controllers because they >>reported what the disk said it was, rather than the "translated" >>numbers that the 34F used (and it was not possible, when last I >>looked, to disable this translation). > >SCSI disks and controllers don't "use" any geometry. Well, most SCSI BIOSes rely on a particular geometry for finding the boot sector, but once FreeBSD is booted, the geometry is irrelevant. >FreeBSD begins with the geometry reported by the drives. For SCSI disks, >I think this still usually has something to do with the actually geometry >(#cylinders and #tracks are correct, and #sectors is the average), but >this geometry is normally neither useful nor used. As of CAM, the SCSI controller driver is provide the total number of sectors reported by the device and converts this to a CHS geometry suitable for a bootable volume. I never really looked into why fdisk and friends don't pick up this geometry when the existing pack information is bogus. >These problems mean that "auto" on a slice can't be implemented properly >without solving the old problem of mapping drives to BIOS drive numbers >so that the table of BIOS geometries can be used. Actually, most SCSI controller drivers can get this right without knowing the BIOS drive number. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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