From owner-freebsd-questions Sat May 30 02:27:57 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id CAA21645 for freebsd-questions-outgoing; Sat, 30 May 1998 02:27:57 -0700 (PDT) (envelope-from owner-freebsd-questions@FreeBSD.ORG) Received: from freebie.lemis.com (freebie.lemis.com [139.130.136.133]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id CAA21634 for ; Sat, 30 May 1998 02:27:45 -0700 (PDT) (envelope-from grog@lemis.com) Received: (from grog@localhost) by freebie.lemis.com (8.8.8/8.8.7) id SAA00338; Sat, 30 May 1998 18:57:41 +0930 (CST) (envelope-from grog) Message-ID: <19980530185741.K20360@freebie.lemis.com> Date: Sat, 30 May 1998 18:57:41 +0930 From: Greg Lehey To: walton@nordicdms.com, freebsd-questions@FreeBSD.ORG Subject: Re: fdisk slice oddities References: <199805140024440448.02FAF632@mailgate.execpc.com> <19980530073409264.AAA277@mail.nordicdms.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.91.1i In-Reply-To: <19980530073409264.AAA277@mail.nordicdms.com>; from Dave Walton on Sat, May 30, 1998 at 12:34:09AM +0000 WWW-Home-Page: http://www.lemis.com/~grog Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-41-739-7062 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Sat, 30 May 1998 at 0:34:09 +0000, Dave Walton wrote: > I was just setting up a new 2.2.6R system, and saw something odd > in fdisk that I haven't noticed before. I'm hoping one of > you can explain this to me. ("fdisk" refers to the interactive > version in sysinstall, not the other one that I don't know how to > use.) > > When I go into fdisk, it reports the disk geometry as detected during > boot: 4960/16/63 > If I tell it to use the whole disk, it keeps that geometry and makes > the necessary slices. But if I tell it to use the whole disk in > dangerously dedicated mode, it changes the geometry to 311/255/63. Dedicated mode. It's not only not dangerous, it's safer than non-dedicated mode. > Is there some particular reason why dangerously dedicated mode > changes the drive geometry? It might come closer to getting it right. We need to completely revise this stuff. Nobody has really looked at it for as long as I've been involved with FreeBSD (about 4 years). In that time, computers have come to accept large disks, we have various mapping models for Microsoft, and we (FreeBSD) need to have tools which can handle the changed situation. I suppose the most important difference is that no modern disks have a rigid geometry any more (in other words, the terms cylinders, heads and sectors are all faked). All we care about is the LBA (logical block addressing) mode. FreeBSD has been doing this for a long time, but we've still been inventing fake geometries for the sake of other systems. It's about time we stopped, but I, for one, don't know what kludges Microsoft has applied. In dedicated mode, this shouldn't make any difference, but if you want to share, there could be problems. Apart from the observation, did you have any problems? Greg -- See complete headers for address and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message