Subject: Strange disklabel/fidsk info?
To: None <>
From: Richard Rauch <>
List: port-i386
Date: 12/22/2000 23:35:13
I have a hard drive that is 20GB (give or take a little).  It is generally
recognized as such by NetBSD.  However, note the following:

 /~~~ dislable -r wd0a

bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 16383
total sectors: 40020624
rpm: 3600

 \___ disklabel -r wd0a

When I multiply 63*16*16383 I get 16514064 total sectors (or, rather,
Octave does, and I trust Octave to some degree (^&).

Partition's c, d, an d e go out through _cylinder_ 39702; that many
cylinders would make sense with the size of the drive, but disagrees with
the supposed geometry.

The above numbers, instead, would correlate roughly to about 7 or 8 GB,
rather than the 20 that I actually have.  Similar results come from fdisk:

 /~~~ fdisk

NetBSD disklabel disk geometry:
cylinders: 16383 heads: 16 sectors/track: 63 (1008 sectors/cylinder)

BIOS disk geometry:
cylinders: 1024 heads: 255 sectors/track: 63 (16065 sectors/cylinder)

Partition table:
3: sysid 169 (NetBSD)
    start 63, size 40020561 (19541 MB), flag 0x80
        beg: cylinder    0, head   1, sector  1
        end: cylinder 1023, head 254, sector 63

 \___ fdisk

Notice that the two different geometries have roughly equivalent
capacities (about 7 or 8 GB).

Could this just be because the place that put the system together
formatted to ~8GB for testing?  (It came with a semi-bootable version of
MS-WINDOWS left over from their testing; I simply booted a NetBSD CD onto
it and never looked back.  I have no idea how they tested it, but it's
plausible that they did so with an 8GB BIOS partition.)

Does this even matter so long as I don't try to boot off of anything past
the first 7 or 8 GB?  (I intend to put GNU/LINUX on a ~4GB sliver, which I
can easily put at the front end of the drive.)  What, if anything, should
I do to fix this?

Basically, when I got the system last August, I put 1.5_ALPHA on it.  I'm
only seeing this peculiarity now, as I'm reading through fdisk(8)'s
man-page to set up a multi-boot with GNU/LINUX and NetBSD 1.5.

As an aside, the drive supposedly does 7200rpm, not 3600.  Is that error
going to cause any inefficiencies in NetBSD's use of the drive?

Thanks in advance.

  "I probably don't know what I'm talking about."