www.grootersnet.nl

Shared SCSI

Computer

Hardware

Have the RIGHT controllers inside. These must be differential-SCSI. Fun part is that you can use long cables - longest in this configuration is 5 m. But shorter is always possible as well.

If the machine is at the end of the bus, be sure to have terminators installed internally!

Beware however that you may run into hardware that is NOT supported. I added a KZPBA in the Personal WorkStation, but ity caused trouble in the AlphaStation200. Here, I use KZPSA instead.

There is another reason for this.

Each system on the shared SCSI bus must have a unique Logical Unit Number - or ID, and that was not the case. This caused the console software to crash as it was set up. You can change it but you need special software to change the non-volatile memory - and I don't have the software. KSPSA controllers can be configured using SRM varilables what makles them great for use instead.

In all systems, this extra SCSI controller is PKB, and both KZPSA's needed their ID changed.

Place a terminator on the connector and boot the system. and SRM variable PKB0_ID is set to 6 in one and 5 in the other:

>>> set pkb0_id=6

or whatever non yet used number (0-7), and switch down the machine.

Now connect the controller to the HSZ50 (directly if at end AND terminated, or using a Y-cable, connecting one to the HSZ50 and the other to the other machine - or holding a terminator to end the bus.

If you switch on the machine, you should see the units as defined.

VMS

Now boot conversational (-flags 0,1).

on SYSBOOT enter:

SYSBOOT> SET DEVICE_NAMING 1
SYSBOOT> SET/CLASS PKB 116
SYSBOOT> CONTINUE

or whatever number is appropiate (1-32767). I used 116...

Cluster_config.com allows this change as well, but you will have to have booted first.

Once the OS is booted, OpenVMS will recognize all units defined - with class $116$ and all on the FIRST controller (dka):

$ SHO DEV D

Device               Device Error Volume   Free      Trans Mnt
Name                 Status Count Label    Blocks    Count Cnt
$1$DKA0:     (DIANA) Mounted     0 ALPHASYS   5433861 1142    1
$1$DKC0:     (DIANA) Mounted     0 WEB_DISK   5993745     9    1
...
$116$DKA100: (DIANA) Mounted     0 AXP082    52227036     7    1
$116$DKA101: (DIANA) Online      0
$116$DKA102: (DIANA) Mounted     0 INSTALL   70386912     1    1
$116$DKA103: (DIANA) Online      0
...

$116$DKA206: (DIANA) Online 0

As can be seen, each can normally be initialized and mounted.

Other nodes

This change of port allocation class must be repeated on EACH node that connects to the shared SCSI bus, otherwise access will fail, and the units will be be accessable at all.