Identical hard drives, different disklabel sectors/cylinders

[wbwither at bobball.uchicago.edu]

Hi all,

I've got a problem question about my hard drives.  I've installed 
two brand-new Western Digital 250GB drives on the same channel of 
a Maxtor-branded PCI/IDE controller (Promise chipset).  I've tried 
different channels, different cables, and using the motherboard's 
IDE controller -- same thing every time.  Here's from 
/var/log/messages:

Dec 18 15:59:23  /kernel: ad4: 238475MB <WDC WD2500SB-01KBA0> [484521/16/63] at ata2-master UDMA100
Dec 18 15:59:23  /kernel: ad5: 238475MB <WDC WD2500SB-01KBA0> [484521/16/63] at ata2-slave UDMA100

So you can see it's identifying them the same at startup.  Now:

su-2.05b# disklabel ad4
# /dev/ad4c:
type: unknown
disk: amnesiac
label:
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 255
sectors/cylinder: 16065
cylinders: 30400
sectors/unit: 488392002
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # milliseconds
track-to-track seek: 0  # milliseconds
drivedata: 0

8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
c: 488392002        0    unused        0     0        # (Cyl.    0 - 30400*)
e: 488392002        0     vinum                       # (Cyl.    0 - 30400*)
su-2.05b# disklabel ad5
# /dev/ad5c:
type: unknown
disk: amnesiac
label:
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 484520
sectors/unit: 488397105
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # milliseconds
track-to-track seek: 0  # milliseconds
drivedata: 0

8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
c: 488397105        0    unused        0     0        # (Cyl.    0 - 484520*)
e: 488397105        0     vinum                       # (Cyl.    0 - 484520*)

So you can see, the "sectors/cylinder", "cylinders", and "sectors/unit"
are all different, and this results in slightly different final sizes.
I've set up vinum to create a mirror using the smaller of the two sizes,
and it seems to be working fine, but I'm still worried about the implications 
of this.  Could this mean that one of my hard drives is failing?  (Again, 
they're both brand new.) I tried "disklabel -R"'ing each drive to look like 
the other one (booting in single-user mode), but it wouldn't let me.  So I'm 
smack out of ideas.  I'd appreciate any info or suggestions.

Thanks,

-Brock Witherspoon