From: julian@tfs.com (Julian Elischer)
Subject: Re: [386BSD] Disklabel for MAXTOR LXT340S
Organization: TRW Financial Systems
Date: Sat, 12 Dec 1992 10:06:20 GMT

In article <1992Dec10.080231.10747@email.tuwien.ac.at> mbirgmei@email.tuwien.ac.at (Martin BIRGMEIER) writes:
>Hello netters,
>
>could those who know please tell me the geometry and other pertinent
>data (disklabel etc) of the following drive type which I'm using under
>386bsd:
>
>MAXTOR LXT340S 6.20
>
>Julian's SCSI driver reports 322MB, cyls 1546, heads 7, secs 61,
>bytes/sec 512 - which yields according to my poor knowledge of algebra
>1546 * 7 * 61 / 2 / 1024 MB of disk space, equal to 322.33496 MB (which
>coincides with the first number given - so far so good).
>
>But why then did the default installation (install.fs) create the following
>disklabel:
>
># /dev/ras0d:
>type: SCSI
>disk: 
>label: 
>flags:
>bytes/sector: 512
>sectors/track: 32
>tracks/cylinder: 64
>sectors/cylinder: 2048
>cylinders: 324              <=========================== (!)
It used the BIOS's idea of the geometry which is different.
(The adaptec sets it up to LOOK LIKE 32sec, 64heads, 324CYL)

in fact since the disk MAY have Zone recording we may BOTH be wrong!
in taht case teh number of sectors per cyl (I give an average)
MIGHT be as high as 61.9999999 but I can only use the integer
61.
This would give an actual size of 335.4MB
( must report a size that gives an integer number of cyls
according to the (obviously ficticious) figures I have
calculated.  therefore I 'lose' about 2MB.)
sorry.. (there may be a better way)

>rpm: 3600
>interleave: 0
>trackskew: 0
>cylinderskew: 0
>headswitch: 0		# milliseconds
>track-to-track seek: 0	# milliseconds
>drivedata: 0 
>
>3 partitions:
>#        size   offset    fstype   [fsize bsize   cpg]
>  a:   653312        0    4.2BSD     1024  8192    16 	# (Cyl.    0 - 318)
>  b:    10000   654653    unused        0     0       	# (Cyl.  319*- 324*)
>  c:   665153        0    unused        0     0       	# (Cyl.    0 - 324*)
>
>Question: Why are there those gaps between partitions a and c, and why is
>there a gap between the end of b and the assumed and of the disk as defined
>by partition c?
no idea.. (That's the install prog at work)

>
>I manually repartitioned the whole thing with the following disklabel (nice
>exercise getting used to the quirks of rdump and rrestore :-)):
>
># /dev/ras0d:
>type: SCSI
>disk: 
>label: 
>flags:
>bytes/sector: 512
>sectors/track: 32
>tracks/cylinder: 64
>sectors/cylinder: 2048
>cylinders: 322
>rpm: 3600
>interleave: 1
>trackskew: 0
>cylinderskew: 0
>headswitch: 0		# milliseconds
>track-to-track seek: 0	# milliseconds
>drivedata: 0 
>
>7 partitions:
>#        size   offset    fstype   [fsize bsize   cpg]
>  a:    40960        0    4.2BSD     1024  8192    16 	# (Cyl.    0 - 19)
>  b:    51200    40960      swap                    	# (Cyl.   20 - 44)
>  c:   659456        0    unused        0     0       	# (Cyl.    0 - 321)
>  d:   659456        0    unused        0     0       	# (Cyl.    0 - 321)
>  g:   567296    92160    4.2BSD     1024  8192    16 	# (Cyl.   45 - 321)
>
>Is this a good thing to do? Obviously, I'm still missing some vital
>data.  For one, I changed interleave from 0 to 1, which seems quite
>obvious. But what should I fill into the remaining unknown fields
>(disk, label, flag, rpm, trackskew, cylinderskew, headswitch,
>track-to-track seek, drivedata)? I assume that the skews are 0 (since
>the drive does internal translation anyway), what about the others? Or
>is it possible to use the drive in untranslated mode (don't think with
>a SCSI)?
>
>So, any help (and numbers) would greatly be appreciated!
>
>Thanks in advance,
>
>Martin Birgmeier
>Technical University of Vienna
>Dept. of Comm. Engr.
>Austria


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