Date: Mon, 20 Nov 2000 09:58:15 +1030 From: Greg Lehey <grog@lemis.com> To: Jason Spencer <jspencer@epsb.net> Cc: stable@FreeBSD.ORG Subject: Dedicated disks (was: Dangerously Dedicated) Message-ID: <20001120095815.H58333@echunga.lemis.com> In-Reply-To: <f04330101b63e03840335@[10.250.1.81]>; from jspencer@epsb.net on Sun, Nov 19, 2000 at 03:40:09PM -0700 References: <3A18304B.689C2CFE@glue.umd.edu> <200011191657.eAJGvnZ63007@cwsys.cwsent.com> <3A180EA0.31926227@glue.umd.edu> <20001119094725.B66448@dragon.nuxi.com> <200011192214.eAJMEPG03693@billy-club.village.org> <f04330101b63e03840335@[10.250.1.81]>
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On Sunday, 19 November 2000 at 15:40:09 -0700, Jason Spencer wrote: > At 3:14 PM -0700 11/19/2000, Warner Losh wrote: >>> We've been successfully using DD mode for years now, if slices are >>> "demanded" what kind of voodoo have we been using? >> >> The problem is the bogus MBR that the DD writes confuses some >> BIOSes and causes your disks to be non-bootable. Right, but you find that out pretty quickly. In my experience, most BIOSes have not been confused. Laptops seem to be the worst. This is really a problem that can be fixed. The argument currently is that it's almost impossible to calculate the correct data, but that's not true: if you can create a partition table, you can calculate it. A real bandaid approach would be to create a correct partition table and then mangle it to make the whole disk dedicated. >>> Is there some way or ways in which the 4-slot table is superior to DD-mode? >> >> The 4 slot table already is there in DD mode. It just happens to >> contain completely bogus data. But it doesn't take up additional space. A real Microsoft layout sacrifices the first "track" and up to a megabyte or so at the end of the disk. >>> You mentioned not having enough space for boot0. Why can't we just >>> change DD-mode to have space for boot0? >> >> Sure, you can do that by putting a proper MBR on the disk :-). The >> whole problem comes in with the bogus MBR that DD puts on the disk. > > So maybe we need to change the docs. When I chose DD mode I thought > "Okay, I'm not going to be using MS *anything* so DD mode will just > reduce some overhead perhaps and make things work like the more sane > platforms." I had no idea that actually I was faking out the BIOS > with bogus data. > > I thought "dangerous" was used in the cute sense of the word ;) It's only dangerous in the sense that it might not work. Once it works, it will continue to work at least until you change the hardware to which the disk is connected. > On a related note, is this anything to worry about? > > $ pstat -s > Device 1K-blocks Used Avail Capacity Type > /dev/ad0s1b 563072 0 563072 0% Interleaved > /dev/rad2s1b 267248 0 267248 0% Interleaved > > One of my swap partitions shows up as a raw device and the other doesn't. I assume you're running -STABLE, in which case that's a benign configuration error: they're both raw devices. Take a look at your fstab and fix the "raw" device entry (rad2s1b -> ad2s1b). Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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