From: root@wsm.com (System Manager)
Subject: Re: Hitachi 3.7Gb SCSI disks.
Organization: Western Scientific
X-Newsreader: Tin 1.1 PL4
Date: Sat, 23 Jan 1993 00:46:24 GMT

mbdtsmc@uts.mcc.ac.uk (M.D.Cooper) writes:
: We have been offered some very cheap (by U.K. Standards) disks. They are Hitachi
: 3.7 Gb SCSI drives and I've been assured by the salesman that there will be no
: problem hooking them up to our HP7[235]0 cluster.
: 
: Does anyone have any experience with these drives?
: 
: Can anyone send me a disktab entry for them which will work?
: 
: 
: Thanks in advance,
: 
: Matt Cooper


Dear Matt,

	BEWARE! The Hitachi DK-517C-37 disks will not work on the HP 9000
700 series systems running HP-UX.

	The 3.7GB drive has a capacity that exceeds the HP-UX's ability
to compute things correctly like disktabs, bootfiles, etc...

	The creation of a bootfile doesn't work for instance if your
loading HP-UX from tape for the first time. The install procedure
looks at the drive and and reads the capacity. The returned number is
so large that the number of 512b blocks * 512 chokes the math register
that the Install procedure uses and replies...

	Cannot load HP-UX to disk drive of -55 MB Capacity
	You must use a minimum 120MB disk drive to load HP-UX

How do you like that> -55 MB disk (Its a black hole, negative disk space)
Its a really great physics trick if it were real.

Anyhow I have been testing the DK-517C-37 for Hitachi on the HP9000/7xx
with HP-UX 8.0.7 using SCSI bus analyzers and using SCSI Mode Select
to decrease the number of cylinders, reformatting it and retesting
the drive. The threshold of PAIN for the Drive on HP-UX was 2.15GB
(Slightly less than 2.9).

	Im sure this will be a problem, even though the Hitachi DK-517
is SCSI-2 compliant, on HP-UX until HP themselves make a 3.5GB disk drive
and write support for a physical disk of that size into a later version
of HP-UX. This error is the same, by the way, for the Seagate Elite 3
3.5GB disk drive.

	I had a posting to this newsgroup regarding the size of the
math register in HP-UX earlier when I was diagnosing thsi problem.
It took the use of a SCSI bus analyzer to figure out what was going on.

	In all fairness to Hitachi, you can guesstimate and contrive
a disktab entry for the drive, run newfs sucessfully, write data to it
and even run mkboot on it. The systems IPL wont recognize the bootfile
on the drive if you reboot. The boot on that drive will fail. The systems
diagnostics (XSTM, CSTM) will not recognize the drive either.

	As a data disk goes, it looks like it works. But the firmware and
the disk is in an infantile stage as of today.

	The questions you must ask are: How often do I backup?
					How valueable is my data?
					And is it worth the cost of
					the DK-517C-37 drives to be
					a Beta site on a foreign shore?


If you'd like proof, I've got what seems to be a couple miles of 
Z-fold printer paper with SCSI bus traces of the DK-517C-37 on the
HP system. If you need reading material to put you to sleep.

-Jeff Johnson
 Dir. of Engineering
 Western Scientific
 Systems and Peripherals
 jeff@wsm.com


Organization: School of Computer Science, Carnegie Mellon, Pittsburgh, PA