Date: Sat, 16 Oct 1999 23:59:44 -0700 (PDT) From: Annelise Anderson <andrsn@andrsn.stanford.edu> To: "Ronald F. Guilmette" <rfg@monkeys.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Some serious gripes about `fdisk' and also `booteasy'. Message-ID: <Pine.BSF.4.10.9910162350540.7187-100000@andrsn.stanford.edu> In-Reply-To: <3113.940136717@monkeys.com>
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On Sat, 16 Oct 1999, Ronald F. Guilmette wrote:
>
> In message <Pine.BSF.4.10.9910162031250.6729-100000@andrsn.stanford.edu>, you w
> rote:
>
> >
> >
> >On Sat, 16 Oct 1999, Ronald F. Guilmette wrote:
> >
> >>
> >> This had bitten me twice now.
> >>
> >> Will whoever is supporting/maintaining the `fdisk' program *PLEASE* fix it
> >> so that it displays some sort of a warning when the user is just about to
> >> partition a SCSI drive for which the on/off status of BIOS address trans-
> >> lation (for disks larger than 1GB) _cannot_ be automatically and properly
> >> determined by fdisk itself?
> >
> >One piece of advice often given is to put a dos partition on the disk
> >(it can be deleted during install if wish) to assist with determining
> >the correct geometry. I've installed FreeBSD on probably a close to
> >a dozen scsi hard drives and never had this problem. I didn't think
> >bios address translation was relevant for scsi drives, in any case.
> >
> >Try the dos partition.
>
> Its too late now!
>
> Yes, if I had known about this trick _before_ got myself into trouble,
> it would have been helpful. But I didn't, so it wasn't.
>
> But anyway, I shouldn't have to stoop to actually handling floppies that
> contain... dare I say it... (yecch, gag) software from REDMOND WASHINGTON!
>
> (I always worry when _I_ have to come into physical contact with such things,
> let alone bringing them into contact with my hard drives. I mean hey, I
> don't want to get CONTAMINATED! Remember what happend to those people in
> that Tokyo subway? This MS stuff is all really icky phoo as far as I'm
> concerned. I'm not kidding. I don't like touching that stuff. It's like
> a disease. It sticks to you, and its tuff to get off, even with a big green
> bar of LAVA.)
>
> More to the point of course, I don't want to waste disk space for an MS-DOG
> partition that I am *never* going to use.
I told you you could delete it during the install, when it has already
done its work.
>
> Even more to the point: This is (apparently) a known ``gotcha'', i.e. the
> fact that the FreeBSD `fdisk' will guess wrong about the geometry of SCSI
> drives and then blithely let you go thru a whole install process with NO
> HOPE of ever being able to boot what you are installing.
>
> This is exactly the kind of place where it would be just polite to put up
> the software equivalent of a big red flashing sign saying ``CAUTION! LAND
> MINE AHEAD! WATCH WHERE YOU STEP!''
As I recall there's some advice about this in install documentation,
which is one reason to get the cdroms and print the stuff (and read it)
before you install. That's what I did.
But here's also a piece from the faq:
<quote>
Chapter 1. Installation
Q: Which geometry should I use for a disk drive?
A: (By the "geometry" of a disk, we mean the number of cylinders,
heads and sectors/track on a disk - I'll refer to this as C/H/S for
convenience. This is how the PC's BIOS works out which area on a disk
to read/write from).
This seems to cause a lot of confusion for some reason. First of all,
the physical geometry of a SCSI drive is totally irrelevant, as
FreeBSD works in term of disk blocks. In fact, there is no such thing
as "the" physical geometry, as the sector density varies across the
disk - what manufacturers claim is the "true" physical geometry is
usually the geometry that they've worked out results in the least
wasted space. For IDE disks, FreeBSD does work in terms of C/H/S, but
all modern drives will convert this into block references internally
as well.
All that matters is the logical geometry - the answer that the BIOS
gets when it asks "what is your geometry?" and then uses to access the
disk. As FreeBSD uses the BIOS when booting, it's very important to
get this right. In particular, if you have more than one operating
system on a disk, they must all agree on the geometry, otherwise you
will have serious problems booting!
For SCSI disks, the geometry to use depends on whether extended
translation support is turned on in your controller (this is often
referred to as "support for DOS disks >1GB" or something similar). If
it's turned off, then use N cylinders, 64 heads and 32 sectors/track,
where 'N' is the capacity of the disk in MB. For example, a 2GB disk
should pretend to have 2048 cylinders, 64 heads and 32 sectors/track.
If it is turned on (it's often supplied this way to get around certain
limitations in MSDOS) and the disk capacity is more than 1GB, use M
cylinders, 63 sectors per track (*not* 64), and 255 heads, where 'M'
is the disk capacity in MB divided by 7.844238 (!). So our example 2GB
drive would have 261 cylinders, 63 sectors per track and 255 heads.
If you are not sure about this, or FreeBSD fails to detect the
geometry correctly during installation, the simplest way around this
is usually to create a small DOS partition on the disk. The correct
geometry should then be detected (and you can always remove the DOS
partition in the partition editor if you don't want to keep it, or
leave it around for programming network cards and the like).
Alternatively, there is a freely available utility distributed with
FreeBSD called ``pfdisk.exe'' (located in the tools subdirectory on
the FreeBSD CDROM or on the various FreeBSD ftp sites) which can be
used to work out what geometry the other operating systems on the disk
are using. You can then enter this geometry in the partition editor.
</quote>
While I have some sympathy with your desire to be warned,
modern computer operating systems are complex and it is
difficult to anticipate everything a user might run into in
the process of installation. I read some documents before I
installed that made me aware that I needed to know a good deal
about my hardware during the process, and I made some effort
to find out about the geometry of scsi drive, all 575 megabytes
of it, and got, from various sources, three different answers.
The above was not available at the time.
Annelise
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