cheapo SCSI disks -- the continuing saga (L

[Steve Harris]

Some time ago, I queried the net if anybody had experiences with "cheapo"
SCSI disk drives.  I received two kinds of responses:

1)  No, but let me know what you learn.

2)  We're using 350 MB disks from XYZ which sell for $2500.

By "cheapo", I meant under (or close to) $1000.  Which probably means
about 80 MB capacity.  Which probably also means targeted for the PC
market.

After shopping around, asking folks at work where they got their PC or Mac
disks, we identified a vendor, Hard Drives International (HDI) of Tempe,
AZ, as having very good prices, a reputation for quality, and a 30 day
free return/replacement policy.

However, they have no experience with Sun computers.  This means, insofar
as support goes, you're on your own!

Here is a sample of the SCSI disks they have (price includes enclosure and
power supply, capacity is in MB, times are in milliseconds):

				Capa-	Seek	Transfer
Manufacturer	Model		city	Time	Rate	Price
------------	-----		---	----	-----	-----
MiniScribe	9380S		340	16	10	1895
MiniScribe	3180S		160	17	10	1275
Seagate		296N		80	28.0	10	599
Quantum		Pro80S		80	19.0	10	799
Quantum		Pro105S		105	19.0	10	899
Micropolis	1375		153	16.0	10	1295
Micropolis	1578		332	16	10	1795

(Note: these prices change, the Pro80S just went down $150!!)

DISCLAIMER -- I have no association with these people other than as a
satisfied customer.

Their phone number is: 800-234-3475.  You get a cheerful recording and
wait for the next available sales rep. (usually not more than a minute).
If you will be buying for your company, ask for Brian in Corporate
Accounts -- he knows his business particularly well, and was most helpful
(give him my name so he knows putting up with me was worth his while).

We ordered the Quantum Pro80S and the MiniScribe 3180S.  The Pro80S is the
little brother to the Pro105S, which Sun uses in the SPARCstation and the
3/80, so I was confident it would work.  I called MiniScribe and they said
they were "pretty sure" their drive would work.

To make a long story short, I never was able to format the MiniScribe, and
returned it.  We'll try the Micropolis 1375 next.

I had all kinds of problems with the Quantum.  But I finally succeeded in
formatting the drive after the manual arrived and I found the actual
number of blocks on the drive.  The entry in the /etc/format.dat file is
WRONG.  Here is the entry I made that works.  

disk_type = "Quantum ProDrive 80S" \ : ctlr = MD21 : fmt_time = 1 \ :
cache = 0x5c : trks_zone = 6 : atrks = 0 : asect = 1 \ : ncyl = 802 : acyl
= 2 : pcyl = 804 : nhead = 6 : nsect = 34 \ : rpm = 3662 : bpt = 16896

# partition table for 11MB root, 25MB swap, and 45MB usr
partition = "Quantum ProDrive 80S" \
	: disk = "Quantum ProDrive 80S" : ctlr = MD21 \
	: a = 0, 22644 : b = 111, 51204 : c = 0, 163608 : g = 362, 89760

FORMATTING THE DRIVE:

After correcting the format.dat file, I used the format utility under
SunOS 4.0.3 on a both a SPARCstation1 and a 3/50.  On the SPARCstation,
the drive at SCSI address 1 is sd1, on the 3/50 it is sd2 (see below).  In
the next couple paragraphs, I will refer to this as drive 1 (as on the
SPARCstation), substitute "drive 2" if on a 3/50, 3/60, etc.

Format goes out and looks for drives attached to the system.  If it
doesn't find sd1, either the addressing or the wiring is wrong.

When you select drive 1, you may get messages to the effect that there are
discrepancies between the size reported by the disk and the size reported
by the label.  Ignore these, you're going to reformat the disk anyway.

You will also get a message that no defect list was found.  Go into the
defect sub-system and request the original defect list, the drive will
report some number of defects to the Sun.  When you exit the defects
sub-menu, commit the new list.  (It's my impression that the disk is smart
enough to take care of its own defects, and that this is why the format
does not find a defect list.  I don't know if it matters whether or not
you extract the original list from the disk, it doesn't show up if you
format the disk again.)

During the course of formatting the disk (which takes about 1 second!),
format reports the following error message:

	Error for command 'format'
	Error Level: Fatal      Block: 3
	Sense Key:      Illegal Request

Warning: Using default mode select parameters.
Warning: Drive format may not be correct.

Block 3 (0/0/3), Fatal non-media error (illegal request) failed

THIS IS A SPURIOUS ERROR MESSAGE, THE FORMAT DID WORK CORRECTLY!

(Thanks to Donna at the Sun hotline for telling me to ignore this error
message, and for being so helpful.  As she noted, the real test is whether
or not the label command succeeds.)

Next issue the label command.  It should work with no errors.  Exit format
and run newfs to build your filesystems. (more: see below)

THE HDI SHOEBOX:

To get the free-standing "shoebox" from HDI, you have to order the "Mac
kit", but need to specify a generic SCSI interface.  It was explained to
me that the Mac SCSI interface is non-standard and requires a different
EPROM than the Generic, or PC, interface.  Later I spoke to Quantum who
said this is not the case (at least for the ProDrives) -- I didn't fully
understand what the difference was but you could use either style equally
well.  For other drive manufacturers this may not be true, so order the
Mac kit with the generic SCSI interface.

The box has two female "CHAMP"-style SCSI connectors on the back (like a
Centronics printer connector).  However, when you look inside the box you
see that they do NOT form a horseshoe loop with the drive in the middle --
the ribbon just runs from the first connector to the second connector to
the drive.  This means you cannot daisy-chain these units!  (You would
have to modify the cable to make a horseshoe).  Since I do not plan to
daisy chain, I just connect to the lower CHAMP connector, the one at the
end of the cable (I'm not a SCSI expert, but it's my understanding that
you must avoid all "T" connections to the SCSI bus -- by connecting to the
middle CHAMP, the little strand of ribbon cable to the lower connector
would constitute a T and signal quality could be compromised -- SCSI
experts please correct/amplify these remarks).

CABLING TO THE SUN:

HDI supplies a cable to connect the "shoebox" to your Mac.  At one end is
a 50 pin CHAMP connector, at the other is a 25 pin "D" connector (like
RS-232).  It's useless!  You will have to buy or make your own cable -- I
make mine with unshielded ribbon cable and 50-pin CHAMP and "D" IDC
(Insulation Displacement) connectors.

For connecting to the SPARCstation, I built a CHAMP to "edge-connector"
ribbon cable, opened up the box and connected the external disk in place
of the second disk.

Some time ago, there was much discussion of how Sun screwed up the SCSI
interface on their 3/60s -- pin 26, which is supposed to supply +5 volts
for termination power was grounded.  This meant that any other device
which chose to supply +5 on that line was likely to melt-down its power
supply, or worse, its firmware.  Since, up till now, I have always
connected to Sun shoeboxes, I have not been concerned with this problem.

However, now that I am connecting to another vendor's shoebox, I must take
precautions.  As a simple, if ugly, fix, I just cut wire 26 of the ribbon
cable at the Sun end, causing line to float.  (Actually, I made a short
piece of cable with line 26 cut which I can insert between the sun and the
cable to the disk drives).  Strangely, when I tested for continuity
between pin 26 and ground on the 3/60, there was none.  Still, better to
be safe...

BTW -- the Quantum drive does not have a jumper to select the source for
termination power (a la CDC).  According to their tech hotline, the
hardware can detect +5 on pin 26 and uses that if it's there, otherwise it
uses +5 from its local power input!

DRIVE ADDRESSING:

Note that the SPARCstation's disk addressing is peculiar -- logical disk 0
(sd0) is at SCSI address 3, and logical disk 1 (sd1) is at SCSI address 1.

On the 3/50, SCSI address 1 maps to logical disk 2 (sd2).  This is due to
the assumption that there can be up to two drives on each SCSI controller
(the SCSI standard allows up to 8 devices per controller); the SCSI
controller at address 0 (my primary drive) could have disks 0 and 1, the
controller at address 1 (my secondary drive) could have disks 2 and 3.  In
fact, with embedded SCSI, there is only one device at each SCSI controller
address, but the Unix kernel is configured to allow for two.

The HDI shoebox has a clever little address setting switch on the back of
the box -- there are two little levers and a window displaying a digit,
press the "+" lever and the digit increments, press the "-" lever and it
decrements (you have to "flip" the lever to be able to press it).

Unfortunately, the value displayed in the window does not match the value
set on the three address jumpers of the drive.  I checked for continuity
and found that setting the switch to 1 does not jumper address A0.
Furthermore, when you examine the wiring of the plug that mounts on the
disks address jumper pins, you see that it can only jumper pins 0 and 1 --
there is only one wire running to the pair of connectors for jumper 2.  (I
assume this setup works okay for Mac's.)

I just disconnected the plug from the disk and set the address manually
(the three address jumpers are labeled: A0, A1, A2).  You have to open the
box up to do this, but once the plug has been removed you can access the
address jumpers by removing a metal plate from the base of the shoebox.

While you're removing the plug, remove the parity-enable jumper (labeled
"PE" -- it's the middle of three, just above the address jumpers).
Apparently the disk doesn't work correctly with the Sun if parity is
enabled (this is at the recommendation of Quantum -- I noticed that the
two Pro105S drives in our SPARCstation also has the PE jumper removed).
(For what it's worth -- I just succeeded in formatting, labeling, and
newfs-ing a Pro80 with parity enabled.)

MANUALS:

The drives do not come with owners manuals -- you can get one by calling
the manufacturer's technical support line.  HDI will give you the
manufacturers' 800 numbers.  Quantum's is 800-367-1984.

Over the course of mucking with these disks, I have looked at a number of
manuals.  Most are fairly good, but usually you have to dig to find the
information you need.  The Quantum manual is exceptional, far superior to
all the others I have seen.  It is well organized, well written, readily
comprehensible (insofar as a technical manual can be readily
comprehensible), and professionally typeset (not a Xerox of an nroff
printout on a dot-matrix printer!!).  There are a large number of diagrams
and tables which make the information much easier to understand.  It has
as good a summary of SCSI as any I have seen.  The day the manual arrived,
it took me about 30 seconds to find the information I needed to diagnose
the source of my problems (the erroneous format.dat entry)!  It's my SCSI
reference manual now.

CACHE:

I did not attempt to format the drive using the standalone diag utility
which comes with SunOS 3.x, but I bet it would work.  However, it seems
likely the on-board cache capability of the drive would not be enabled --
there is no provision for this capability in diag.  From reading the disk
manuals, it seems this capability requires a a bit be set in the SCSI
"mode select" command -- it is NOT on by default.  I assume that the
"cache = 0x5c" parameter in the format.dat file results in the appropriate
bit being set.

		=== MILD FLAME ===

I do wish Sun would publish definitions of these parameters (cache,
trks_zone, atrks, asect) so that we could take advantage of them.  For
example, the MiniScribe manual speaks in terms of alternate sectors per
cylinder (not per track); how do I modify my format.dat entry to
accommodate this capability?  Why is there no entry in section 5 of the
Command Reference Manual for format.dat???

		=== END FLAME ===

SUN HOTLINE:

I'd like to take a moment to commend Sun on improving the hotline.  Six
months ago my request for assistance could have taken several days before
I received a response, and it's unlikely the person at the other end would
have been much help.  They have come a long way from those dark days --
the response was within 2 hours, and Donna was most helpful in resolving
this problem.

I'm sure there are still problems, especially with more esoteric aspects
of the operating system.  Nevertheless, I was impressed with the
improvement.

FOLLOW-UP:

Although my formatting took place under SunOS 4.0.3, our application
currently runs under 3.5.  I figured, no problem, I'll just load 3.5 (from
my master tape -- I refuse to go through suninstall) while I still have
the disk mounted under 4.0.3, halt, set the address jumper to 0, plug it
in to a standalone 3/50, and reboot.  No such luck.  I got the message:

	Boot: sd(0,0,0)

and nothing else.  It just sat there.  The EEPROM saw the disk, but was
unable to find the boot program.  Back to the drawing board.

So, I set up a 3/50 with a cartridge tape drive and this disk on the SCSI
bus.  Booted from 3.5 tape, loaded diag, relabeled the disk, loaded the
standalone copy, copied the miniunix to sd(0,0,1), and booted
sd(0,0,1)vmunix -as.  Standard stuff.  Worked fine.  Reloaded 3.5 from my
master tape, sync'ed the disk, and rebooted.  No problem.

Clearly, something under 4.0.3 is incompatible with 3.5.  My guess is
newfs, but how the boot EPROM loads the boot program from the root file
system is a mystery to me.  Any ideas?  

-- Steve Harris -- Eaton Corp. --
Beverly, MA -- uunet!etnibsd!vsh