SUMMARY: different Exabyte densities

From: Rolf Wilson (
Date: Mon Dec 02 1991 - 17:58:50 CST

I would like to thank the following people for replying:

The general consesus is that the standard Sun driver does not handle
writing 8200-readable tapes on an 8500. A workaround is to use a
tape that has been previously written on with an 8200. There are
third-party drivers available, and one person sent a kernel patch
that I have not tried. The editted responses follow --

>From Tue Nov 26 10:32:39 1991

     Get someone to write on the tape once with a 8200 and then your 8500
will write them as 8200. Likewise, once you write them as 8500 you will
need to demagnetize them (haven't tried this though) to make them 8500 tapes
>From kensmith@cs.Buffalo.EDU Tue Nov 26 10:38:07 1991

Yes. It requires kernel patches, and which files need patching depends on
which machine architecture you've got the drive hooked up to. What model
SUN is it on?
>From Tue Nov 26 10:48:45 1991

The tapes need to have the BOT initialized to the lower density.
This is done by writing to the tape with the exabyte 8200 first.
This is assuming you are using new tapes. If you have old tapes
that you have written to using the 8200, this is a moot point.
Conversely, if you write to the new tape using the 8500 exabyte,
the tape (BOT) will be initialized using the default higher density.
You will not be able to read the tape using the 8200 tape afterwards.
We have tried de-magnetizig tape in order to reintialize them. This
didn't work for us.

Also, we use the SunOS 4.1.1's dump utility. The recommended dump
parameters work just fine for the 8200 and 8500 exabyte drives.
>From Tue Nov 26 10:50:24 1991

        Both 8200/8500 tape manipulation are SUPPOSED to available with
        the 8500 unit. Check the operations manual. We have a couple of
        8500s here and they behave as such.
>From kensmith@cs.Buffalo.EDU Tue Nov 26 11:01:31 1991

I've tested this on SUN-4/300's but I'm told it works with the SS-1's too.
The kernel file that needs to be patched is different for the 4/300's than
it is for the sun4c's. For the SparcStations you need to edit the file
/usr/sys/scsi/targets/st_conf.c and change the section that looks like
this :

        /* Exabyte 8mm cartridge */
                 "Exabyte 8mm Helical Scan", 7, "EXABYTE", ST_TYPE_EXABYTE, 1024,
                 5000, 5000,
                 { 0x00, 0x00, 0x00, 0x00 },
                 { 0, 0, 0, 0 }

to make it :

        /* Exabyte 8mm cartridge */
                 "Exabyte 8mm Helical Scan", 7, "EXABYTE", ST_TYPE_EXABYTE, 1024,
                 5000, 5000,
                 { 0x00, 0x00, 0x14, 0x14 },
                 { 0, 0, 0, 0 }

Reboot with the new kernel. Now, assuming your exabyte is rst1 then
writing to rst1 and rst9 will give you high-density mode (5.0 Gbytes)
but writing to rst17 and rst25 will give you low-density mode.

Good luck...

>From Tue Nov 26 11:18:55 1991

We have a TTi 8501 which is probably similar to an Exabyte 8500. To write low
density tapes compatible with an Exabyte 8200 there is a dip switch on the
back of the unit which must be set to force it into low density (2.3 Gb) write mode.
Do you have an owner's manual ? (The manual for the TTi 8501 states that this can
also be done through software, but I do not know how yet.)
>From Tue Nov 26 11:23:42 1991

Something that I heard (but haven't tried):

The 8500 looks at the tape when you load it and switches modes 82 -> 85
or 85 -> 82 if the tape has been written to. Therefore to write in 8200

1) Get an old tape that has stuff written on it with a 2.3GB drive.
2) Put it in the drive.
3) Take it out.
4) Put in a new tape.
5) write to it with tar, dd, dump, whatever...
>From Tue Nov 26 12:29:19 1991

The only way I know of doing this is to write on the tape with an 8200
first. Then the 8500 will recognise it as a low density (2.3G) tape,
and write in low density.
>From lemke@MITL.COM Tue Nov 26 12:38:05 1991

I have done it here on my 8500 attached to a Solbourne S4000.
To write in 8200 mode, I specify /dev/rst0. To write in 8500
mode, I specify /dev/rst8. I do not know if a similar thing
exists on Suns, but it's worth a try (you can test this out
if you have an 8200--try writing something on the 8500 and
then reading on the 8200).
>From vanandel@rsf.atd.ucar.EDU Tue Nov 26 13:05:10 1991

If you buy a 3rd party tape driver, from APUNIX or DELTA microsystems, you can
open a special device (APUNIX) or issue an ioctl (DELTA) to produce 8200
format tapes. I've done it and it works just fine.

I've attached a summary I prepared of info regarding 3rd party exabyte
Subject: SUMMARY- exabyte drivers and CORRECTION
Date: Wed, 18 Sep 91 13:42:15 -0600

Well, the replies have stopped coming in, so here's my summary. My original
>I recently found that the standard Sun driver in SUNOS 4.1.1, on SPARC
>workstations doesn't support high speed search for file marks on the 8500 (not
>surprising, since is was only written for 8200 drives). The result is that
>skipping forward by 50 files takes 10 minutes, rather than 25 seconds. I'm
>trying to choose a 3rd party driver.

I also neglected to mention a driver from R-squared (303-799-9292), which
worked, but had the following drawbacks, when I last tested it.

1) Only worked on desktop SPARCS, didn't support deskside servers like Sun
2) Poorly packaged. Installation instructions didn't work.
3) No utilities to set drive mode, get error statistics, etc

The only other responses I got were about Delta and APUNIX.

(As I said before, Sun Microsystems says that they may support the 8500 by
the end of the calendar year.)

In my original query, I accidently switched the descriptions of the Delta and
APUNIX drivers. Sorry about that!

        Delta Microsystems

        costs ~$450/each for quantity 10, includes graphical performance
monitoring utilities, driver delivered as binary only, customer pays software
maintenance after 1st year. Driver supports a "status only" device that is
used to get drive performance and error statistics while the drive is in use
by another task

        site license ~$5000 for >10 machines, driver source included,
perpetual technical support for no additional cost, driver costs ~$25 if
ordered with Exabyte drive. Includes a utility to backup multiple machines to
the same drive from cron job. Have just added a "status only" device , that
allows you to get drive statistics while the drive is in use by another task.


Here are the comments I received:
From: (Ray Bovet)

I tried out the APUNIX driver long ago when we were first trying to get
Exabytes to run on Ciprico SCSI adapters. I believe that APUNIX has good
technical expertise in house and has probably done a good job. I checked
into it again sometime within the last year.
From: (Emmanuel M. Paul)

        I ordered the Delta smt7 driver to use with an Exabyte 8500 on a SPARC
station 2. When I installed it I started to get sense key errors. Turns out
that DELTA does not approve of the way SUN has implemented syncronous SCSI,
and so their driver disables syncronous mode. Needless to say the other
syncronous devices on the bus no longer function properly. I have had to move
my drive to an SLC. I am still experiencing some incompatabilties between the
EXABYTE firmware and the Delta driver, so I cannot comment on performance as
yet. However the Delta driver seems much more robust than the standard SUN
driver, and so worth using.

(Note- I'm using the Delta driver on a 8500 on a SPARC2 without problems now
that I'm using the 8500 CFT03F2 firmware, but I took pains to keep the SCSI bus
very short!)

From: Jim Mattson <mattson@cs.UCSD.EDU>

A year ago, I would have cautioned you against buying the APUNIX driver,
since we were having nothing but problems with our APUNIX driver for an
exabyte on a Ciprico 3500 Series SCSI to VME controller (Sun 4/280). Our
problems finally seem to have been resolved, but it took APUNIX the better
part of a year to fix everything. Perhaps now it is stable, but it sounds
to me like you are getting a different driver from them. I'd certainly ask
for references of other sites using the same driver you plan to buy.

From: (Brian Keves - Consultant)

I do not know of another company but I can definitely recommend Apunix. I
once had a device driver class at UCSD that the owner and founder of Apunix,
Steve (?Peter?) Berens, gave and he definitely knows his stuff.

From: Brian Kelley <dgsi!euler!>

I've dealt extensively with APUNIX and am extremely pleased with their
service. I use their Exabyte drivers on our SPARCS. They really have their
act together. I haven't found anyone with better tech support when it comes
to Sun SCSI products. I haven't tried the Delta Microsystems products. I
have dealt with quite a few VARs, however. I have very little interest in
dealing with anyone else. [I'm just a happy APUNX customer]

From: kpc!!cdr@uunet.UU.NET (Carl Rigney)

We're using the Delta Microsystems driver for the 8500, and it seems OK.

I've never used the APUNIX driver.
From: Russell Ruby <russ@MATH.ORST.EDU>
Delta never included source during the time i dealt with them, so instead
we played the hassle game of waiting for replacement binaries for bug
fixes and repairs for petty (but devastating) problems which occurred
every time Sun had an OS level revision ...

At my current location we have an 8200 and get by just fine
with the vanilla Sun 4.1.1 driver, but we do use the APUNIX backup
software, no muss, no fuss, just change the tape once a day...
The nice thing i liked about having the source is that i was able
to fix a couple of bugs on the spot when i installed it over a year
ago - sent APUNIX the patches - i'm happy - they're happy - gee
everybody is happy - and it is real nice having the source code ...


Thanks again for all the feedback. I've just ordered 1 copy of the APUNIX
driver to evaluate, and I'll be making my decision on which driver to recommend
in the next month or so. I'm leaning towards the APUNIX driver, because
they'll site license us, and we get the source code.

        Joe VanAndel
        NCAR - ATD/RSF
        P.O Box 3000 Fax: 303-497-2044
        Boulder, CO 80307-3000 Voice: 303-497-2071

        Joe VanAndel
        NCAR / RSF
        P.O Box 3000 Fax: 303-497-2044
        Boulder, CO 80307-3000 Voice: 303-497-2071
>From Tue Nov 26 13:16:28 1991

You will probably get lots of responses about this but here's mine. There
are two ways to accomplish this (writing in 8200 mode on an 8500). The first
is to get a driver that understands the 8500, such as the driver sold by APUNIX.
The driver will issue a special SCSI command that puts the 8500 into 8200
mode (typically based on the minor device id you use). The other way is to
get ahold of Exabyte's PC software that lets you configure an Exabyte 8500
so that it's default mode is 8200 for writing. This also requires a special
cable from the PC's serial port to a special connector inside the Exabyte.
This approach is really only useful if you want to change the default once
and for all.

I hope this helps!

>From Tue Nov 26 13:59:51 1991

The method depends on the particular SCSI tape driver you are using.
If you are using the standard Sun "st" driver, you probably can't
tell it to write in 8200 mode.

Dan Strick, aka or bellcore!dan, (201)829-4624
>From Tue Nov 26 15:08:14 1991

Can't do it ... the tape heads are narrower, and the tracks can't
be read by an 8200.
>From Tue Nov 26 16:14:00 1991

You might try giving Exabyte a call; they're on an
WATS number in Boulder, 800-445-7736. They may have
a generic answer.

Who is the VAR involved? We have the Delta Microsystems
5000 bundle with Budtool. Just in case yours is from the
same place, I called them about this, and will let you know
what I get back.
>From Tue Nov 26 16:31:25 1991

        If you have the Delta Microsystems 5Gb drive, you can
apparently use the command 'drivemode -t /dev/nrstX 2' to set
2 Gb mode, then use it with a 5 to set it back for 5 Gb mode.
>From eric@mpl.UCSD.EDU Tue Nov 26 16:39:20 1991

Exabytes are capable of doing this. But they need to be sent
the proper mode select command. Therefore the question to ask
is does your (Sun?) SCSI driver support this.

>From Tue Nov 26 16:44:32 1991

        I would be very interested in a summary of the responses you receive from your query.
        Recently I posted a query about backup devices with a capacity of greater than 2.3Gb, as we have a couple of EXB-8200s but are quickly outgrowing them. Everyone who responded said the EXB-8500 was OK. I've been doing some additional digging and testing and our requirement is one of redundancy ie. we'll probably buy 1 EXB-8500 but want to use it as a pseudo 8200 until we can get a second (the fun of budgets). I've tried writing a tape on an 8200, it can be read OK on an 8500, we then used the same
and dumped a file-system onto it using the 8500 and tried reading it using an 8200 - FAILED. I've asked one of our local suppliers if there are different command line options you need to use, but I haven't got a reply as yet. In writing the tape using the 8500 we used the same parameters as if it were an 8200 ie.

        dump ${level}ubdsf 126 54000 6000 ${filesystem}:/dev/exabyte

Anyway, I'd appreciate any comments you may have.
>From mark@maui.Qualcomm.COM Tue Nov 26 16:47:53 1991

        We have one of these drives. We purchased it from APUnix. The 8500
    we have will automatically sense the density and we can force the drive
    to read and write 8200 format tapes.

        APUnix (619) 492-2992
>From tres@roke.rap.ucar.EDU Tue Nov 26 16:54:36 1991

        In fact, with the Sun st driver, all you can write are EXB-8200
format tapes. We received a third party driver with our 8500 (R Squared)
which is not the greatest, but seems to work Ok, and allows us to write
EXB-8500 format tapes.
>From ross! Tue Nov 26 19:06:53 1991

All vendors I have talked to claim that the 8500 can read but NOT write in
the 8200 format.
>From barryt@Aus.Sun.COM Tue Nov 26 19:38:43 1991

The new drives are smart enough to determine the format of the tape and will switch accordingly.

This works so well that if you want to store data at 5Gb on a tape that has been written to at 2.3Gb, you will have to erase the begining of the tape first.
>From deltam!dm!mark@uunet.UU.NET Tue Nov 26 21:51:17 1991

I am a Software Engineer at Delta Microsystems. I do not work in the
sales department, nor do I have any connection to that part of the
operation. The information I am about to provide is in response to
your request for information, and should not be taken as an
advertisment for Delta products.


It can be done if you have a driver that is capable of shipping the
proper mode select to the drive. Currently the Sun driver does NOT
have this capability.

I do not know if there are others out there, but the driver available
from Delta can do this. It is done through a modification to our
driver along with a utility program that runs in user space.

Please note, that in order for this to work, the 8500 must have the
latest firmware from Exabyte. I don't know exactly how to tell if
your drive does have this firmware, but I can find out if you need me

Please let me know if you would like any further information. You can
call me on the phone if you wish, or reply by e-mail. Either way, I
hope that the information provided is accepted in the manner it was

--Mark Galbraith Voice: +1 510 449 6881--
--Software Engineer UUCP: uunet!deltam!mark--
--Delta Microsystems, Inc. Domain:

>From james@Solbourne.COM Wed Nov 27 08:20:30 1991

What hardware are you running on? If it is a Solbourne, you need at least
OS/MP 4.1A. Then you just access the lowest /dev/rst# for the drive
to write in 8200 mode (the next st# up is for 8500 mode).

James B. Davis, Consulting Engineer
Tactical Engineering Dept., Solbourne Computer, Inc.
Phonenet: (303)772-3400 x792 Faxnet: (303)772-3646


Rolf Wilson Illinois State Geological Survey

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