From: se@IKP.Uni-Koeln.DE (Stefan Esser)
Newsgroups: comp.sys.dec,comp.unix.ultrix
Subject: Re: Problems with 3rd party disk, HELP!
Date: 7 Apr 92 19:42:46 GMT
Organization: Institute of Nuclear Physics, University of Cologne, Germany

In article <1992Apr6.130522.17343@cs.hw.ac.uk>, raz@cs.hw.ac.uk (Ross A Macintyre) writes:
|> I am having BIG problems trying to get a 3rd party disk working.

|> I got the values for ns, nt and nc from rzdisk, in particular
|> 	rzdisk -g current /dev/rrz0a
|> 
|> (Isn't it strange that 81*15*2179=2647485, and I have pc# = 2606400 ?
|> Well I am told by DEC that this is ok. Normal.)

What does rzdisk tell about alternate sectors of your drive ?
This is what I get for an Fujitsu M2266:

Page 3 - direct-access device format parameters:
  PS                                    1
  Page code                             3
  Page length                           22
  Tracks per zone                       15
  Alternate sectors per zone            3
  Alternate tracks per zone             0
  Alternate tracks per volume           15
  Sectors per track                     85
  Data bytes per phy sector             512
  Interleave                            1
  Track skew                            8
  Cylinder skew                         21
  Flags                                 0x4

You have to subtract the alternate sectors from what you get 
by simply multiplying the drive geometry parameters !
In my sample above, there are 3 alternate sectors per cylinder
resulting in 3 * 1656 alternate sectors, plus an additional 
15 tracks (= 1 cylinder).

So there are 6243 alternate sectors on this drive.
Other SCSI drives come with one alternate on each track, 
resulting in much more wasted space (but for complicated 
reasons better performance with the Berkely Fast Filesystem
which is used in Ultrix).

A first guess is, that your drive has 1 alternate sector per track
plus 7 cylinders of additional alternate sectors.

I'd expect 'rzdisk -g current' to show the following data for your drive:

  Tracks per zone                       1
  Alternate sectors per zone            1		(nas = 1)
  Alternate tracks per zone             0
  Alternate tracks per volume           105	(nat = 105)

(nc - nac) * nt * nas	= (2179 - 7) * 15	1 = 32580
nat * ns			= 105 * 81	  =  8505
					    =====
total alternate sectors:			    41085

2606400 + 41085 = 2647485 ...

|> I put this on the disk, using chpt(with correct options), newfs'd the a partition,
|> put it on again with chpt -a, and newfs'd every partition.
|> Sometimes when I fsck the a partition immediately after it says
|> BAD SUPERBLOCK, use another superblock. I have then seen it work on block 32(but not
|> always), and if I then check it again it with no b option, if fails, and then fails next
|> time I specify block 32 again.

Are you still using Ultrix 4.1 ?
The symptoms are typical for the >1GB problem present in most vendors' 
SCSI device drivers one year ago ...
There is no cure except upgrading to (err, installing of) Ultrix 4.2 ...

STefan
-- 
 Stefan Esser,  Institute of Nuclear Physics,  University of Cologne,  Germany
 se@IKP.Uni-Koeln.DE                                           [134.95.192.50]
Newsgroups: comp.sys.dec,comp.benchmarks