Resolution for DLT 7000 drive on AIX 4.2.1

Resolution for DLT 7000 drive on AIX 4.2.1

Post by Christine R Coope » Thu, 22 Apr 1999 04:00:00


In March I wrote a post on how I was unable to see my DLT 7000 drive on my
AIX 4.2.1 bus.  The drive was a fast wide diff DLT 7000 drive and my server
was a 7013 model J40.

I had two open MD68 connections on the back of my System Card (I.e. the card
that has the keyboard, mouse, and serial connections) and the assumption by
the previous System Admin (and myself also) was that you should be able to
plug into one of these connections, select an unused SCSI ID and properly
terminate the bus.  The expectation was that the drive would show up when
configmgr  was run.

When I came on the scene and inherited the "problem" I was thinking that I
didn't properly understand the relationship between ascsi0, vscsi0, and
vscsi1 and I had posted some questions etc..

Well, we had a very serious crash about a week ago (lost rootvg) and had to
have some hardware switched out.  While the IBM hardware guy was there I
decided to educate myself further on the J40.  I must say, it was quite a

It seems that the two MD68 connections on the back of my system board were
not free (I knew that internal devices were using them but I thought I could
chain)! and that I was NEVER under any circumstances to plug anything into
these connectors.  It appears that the first connection, labeled
differential SCSI A is used for the internal bus (in my case, 4 hard disks,
a CDROM, and an 8mm Tape drive).  The only thing to be attached to this
connection is a Terminator.

The second connection, labeled differential SCSI B, leads to a set of 4
(empty in my case) drive bays where you can put additional disk. Since I had
no disk  installed I was to leave this connection unterminated until such
time as I used one of the empty bays.

Conclusion, I cannot use the built in differential SCSI card (ascsi0) for
anything except to load up the "built in" device bays.  I had to buy a new
fast wide differential card in order to begin the process of adding new FW
diff devices to my system.

I don't know if this is the same on other "classic" RS/6000 hardware but I
must say I found it beyond strange coming from other UNIX vendor shops where
an empty SCSI slot usually means the ability to chain additional device
provided you have a free SCSI ID available.

Oh well, live and learn.  I just thought I would pass this bit of trivia on
to other J40 users.


1. DLT 7205-311 (DLT 7000) settings


I have installed a DLT 7205-311 (IBM's version of a DLT 7000) on my 7013
J40 server.  The drive was seen on boot up and shows a good status:

mode          yes   Use DEVICE BUFFERS during writes  True
block_size    0     BLOCK size (0=variable length)    True
extfm         yes   Use EXTENDED file marks           True
ret           no    RETENSION on tape change or reset True
density_set_1 26    DENSITY setting #1                True
density_set_2 27    DENSITY setting #2                True
compress      yes   Use data COMPRESSION              True
size_in_mb    35000 Size in Megabytes                

I have been noticing several problems:

1) I place a DLT Compat IIIXT tape in the drive and then try to perform
a tar using:

tar -cvf /dev/rmt2 /

About half way through I get a "tar media surface is damaged" followed
by a Tape_ERR1 message in errpt.  I open a brand new tape and try the
same thing and get the same error.  This is not bad tapes because I can
then use these tapes on another system and I good backups.

It should be noted that the light on the tape drive shows the correct
density 15GB.

I tried various block sizes like -b 128 etc.. and could not get a tar to
complete with the compact IIIXT tapes in the drive

2) I try to put a compact IV tape in the drive.  The 20GB light comes on
(should be 35 shouldn't it?)

I then perform various tar's and other activities and they work.

Anyone know why the DLT IV tape shows up only with a 20GB size?  
Any special settings I need to change to in order to use the IIIXT

The only notice I have seen is that when you are using IIIXT tapes you
need to change Density Setting 1 to 25 (I got this from the AIX 4.3 on
line documentation).  I am currently running AIX 4.2.1.

Christine Cooper

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