Date: Sat, 28 Jan 1995 16:06:58 -0600 (CST) From: "Clay D. Hopperdietzel" <hoppy@appsmiths.com> To: hackers@FreeBSD.org Subject: Re: >1024 cyl IDE drive Message-ID: <199501282206.QAA05213@anvil.appsmiths.com> In-Reply-To: <9501281827.AA01957@squid.umd.edu> from "Fred Cawthorne" at Jan 28, 95 01:27:05 pm
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:: Ummm... Why can't you just rewrite the MBR with fdisk or something?? :: I just installed a 1 gig Western Digital drive, and indeed Ontrack Disk :: manager does write some stuff into the MBR... The bios has the real :: parameters in it, so I would guess if this boot code wasn't there, you :: could just use the real ones with the usual >1024 cyl. precautions. :: I didn't check if the translator thingie was installed on the drive :: right out of the package, but I would guess it wasn't. :: If you install a small dos partition, and then try to install FreeBSD, :: then I would imagine it would choke when the MBR is overwritten by the :: boot selector... ): :: There should be a section in the install notes about these drives.. :: :: Fred. :: :: Since I had things apart already, I decided to have a little sick phun messing with this thing and see what would happen if I played dumb installer (not much of a stretch for me, actually ;>). Maybe some of this can be useful for the install notes/documentation project somehow. The software that I have is called EZ-Drive, by Microhouse Intl. I guess the On-ramp stuff might be another species. I installed EZD, selected 2 partitions (telling it the size was not an option). It blew goop out on the drive, copied some system files, etc. Reboot. The EZD banner now comes up. Boots from HD. Run FDISK. I have a 410M primary dos, and a ~410M extended dos with one drive defined. I don't like this. I use fdisk to delete the extended dos partition, give myself a 120 MB primary dos partition (I presume as the D.I. that I now have 600MB for FreeBSD). I fill it up and play with it, and all seems well. Just to be a jerk, I do a fdisk /MBR to see if I can scare EZD away. When I reboot its still there. (perhaps its not the MBR its messing with)? Onto FreeBSD install. I try using the (EZD floppy boot-o-matic) to boot the FreeBSD installation floppy (the ctrl-key hold trick). The FreeBSD floppy will not boot (just spins forever). Ok, I'll boot without EZD. That works. Install comes up. I get to the fdisk part of Install. When I look, I see that it thinks that there is a bootable partition 0, of unknown type, from (0,0,1) to (749,7,17). Also partition 2, (413,0,1) to (824,31,63), also unknown. Huh? Either this is some remanents of the *origional* 50/50 split that the EZD installer did, or FreeBSD fdisk can't cope without the mapper, or this turkey moved where the fdisk stuff lives. The geometry reported was wrong too. In fact, I went through this a couple of times, and I saw 2 different reports, total blocks constant, adjust #heads, #cyls inversely w.r.t each other. Ok, while I'm here I'll write the manager and the MBR from FreeBSD fdisk. Splat! I reboot. C drive now unbootable -- big surprise. Use DOS fdisk again. Shows 50/50 split. Okay, that one's toast. ------ Now I'll forget about the mapper. I boot from floppy, and go to fdisk the drive (without EZD). Fdisk seems to think its a 504MB drive, which is close to the proportion of (1024/1652)=(X/820). Fdisk has enough brains to not try to let the partition extend beyond c=1023. I make a small dos partion as above, and go for the FreeBSD install once again. No problems. Everything seems fine. ------ The other way I setup this drive was as wd1 in FreeBSD, and used the whole thing that way. Obviously no boot shennanigans here. ------- As far as the installation notes are concerned, what I guess I learned from this excercise is: 1 You will *not* run EZD and FreeBSD together, unless you do some very sick and creative things to boot FreeBSD using something other than the boot manager which comes with the install. The FreeBSD boot manager and the mapper would need to sit in the same chair on the C: Drive. 2 Because of 1, you will not get a DOS partition > 1024 cylinders to exist on your system on either IDE drive. 3 If you have EZD, you should remove it before running FreeBSD. When you remove it, you are going to roast any partitions which are already there. 4 There is a caveat surrounding where the large disk is .vs. where the mapper goes. I could imagine a configuration where the C drive was < 1024 cyls, and the D drive was > 1024 cyls. The mapper will still land on the C drive, just to map the D drive. Assuming exception from #2 above based in this is an error. 4 If you are trying to maximize DOS disk space on IDE disk(s), you would do so by laying out your/both IDE drive(s) such that the DOS partitions begin on Cylinder 0, and end on Cylinder 1023. DOS FDISK will prevent you from exceeding cylinder 1023 (at least my version did). 5 FreeBSD doesn't give a good hoot about any of this brain-damage. It'll use the disk just fine, no matter how you configure its partition. ---- an' that's all I got ta say 'bout dat.
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