Date: Mon, 20 Nov 2000 17:40:28 +0100 (MET) From: Helge Oldach <Helge.Oldach@atosorigin.com> To: imp@village.org (Warner Losh) Cc: grog@lemis.com, samz@oz.net, stable@FreeBSD.ORG Subject: Re: Dedicated disks (was: Dangerously Dedicated) Message-ID: <200011201640.RAA15704@galaxy.de.cp.philips.com> In-Reply-To: <200011200019.RAA16004@harmony.village.org> from Warner Losh at "Nov 19, 2000 5:19:43 pm"
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Warner Losh: >In message <20001120095100.G58333@echunga.lemis.com> Greg Lehey writes: > As far as I know, there has been no decision to remove dedicated mode. >: I for one would strongly oppose it. Arguments about bootstraps and >: BIOS are bogus: on a dedicated machine, you only need a bootstrap on >: the boot disk, so any additional disks can always be dedicated. But >: to answer your question: if you have to change from dedicated to a >: Microsoft compatible layout, yes, you'll have to rebuild all your file >: systems. > >No it isn't bogus. You can't boot off a DD disk on some machines >because the MBR is too bogus for the BIOS to cope with. > >The problem with DD is that we put a bogus MBR onto the disk. All >that is necessary to fix it would be to put a non-bgous MBR onto the >disk. If I'm not mistaken that's a contradiction. PC BIOS architecture demands that the first cylinder is not to be used. But obviously DD mode will use it. So what do you put in a non-bogus partition table? If it says the first slice starts at cylinder 0 you still have a broken MBR. If it says it starts at cylinder 1 you are stuck with inconsistency, as cylinder 0 is in fact in use. Seems to me that DD's bogus MBR can't be properly and consistently fixed. Helge To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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