Date: 14 Jan 2003 15:11:48 -0800 From: swear@attbi.com (Gary W. Swearingen) To: Ian Dowse <iedowse@maths.tcd.ie> Cc: Mike Meyer <mwm@mired.org>, freebsd-questions@freebsd.org Subject: Re: Dangerously dedicated vs. fully dedicated, etc. Message-ID: <h7k7h7uy17.7h7@localhost.localdomain> In-Reply-To: <200301141936.aa93359@salmon.maths.tcd.ie> References: <200301141936.aa93359@salmon.maths.tcd.ie>
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Ian Dowse <iedowse@maths.tcd.ie> writes: > At the risk of adding to the confusion, here is a less wordy > description of the various disk layouts. The term `dangerously > dedicated' seems to be used to refer to either options (B) or (C), > so I will avoid using that term: You've cleared up several things, thanks. (I still don't see why any BIOS would have trouble with a DD disk, leading to DD's deprecation, but I can just take people's word for it, for the task at hand.) BTW, I've seen both of your options referred to as DD, if I understood it right. > (A) Normal sliced disk (assuming sectors/track = 63) > > sector 0: boot0 and the DOS slice table /boot/boot0 has the FreeBSD bootloader. The installer also offers to use the "standard" /boot/mbr. > > (B) Dedicated format created by sysinstall ... > sector 1: disklabel > sector 2-15: boot2 Roughly speaking. /boot/boot2 is 15 sectors; I suppose the first (all zeros) is replaced with the disklabel, loosely speaking. The installer (and its code) calls this a DD disk. > (C) Dedicated format using dummy slice ... One such as would be created by "disklabel -B". (/boot/boot1 seems to have the fourth slice pre-defined.) This differs from "B" only in the slice table, right? The "disklabel" manpage implies that this is a DD. It seems that a DD disk is one which is similar to a single slice starting at sector 0, regardless of what the slice table part of sector 0 contains. With FreeBSD-standard boot code and some BIOSes, one disk layout (ie, DD or sliced) will work better than the other. (And for DD disks, some slice table contents might work better than others. I've not read anything comparing your "B" and "C" or either with a slice table full of zeros or random bits.) Thanks again. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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