  shared DSSI disk ISE cluster configuration? 
 The Question is:
 
We are running a 4000 model 300 with an attached R400X.  We have 4 RF31s and
3 RF72s, with the CPU cab and the the top row of the R400X being filled.
 
When I do a show dssi from the console (the &gt;&gt;&gt;) prompt, it shows some of
the drives on bus A and others on B.  I have the drives set to allocation
class 1.
 
VMS shows all drives as being attached to bus A.
 
i.e. $1$DIA0 etc
 
I need to add 3 more RF72s to the R400X, and would like to continue to be
able to ref the drive by a logical name - such as DIA0, DIB0 etc rather than
the node name.  Makes it easy to swap drives by just changing the id plug on
the drive.
 
How do I do this?? (Unfortunately the hardware manuals for the 4300 and the
R400X have disappeared).
 
Also we currently have the R400X connected to the DSSI connection on the CPU
panel.  Should we be reconfiguring this?  I believe that currently the CPU
frame drives are on one bus, and the R400X drives are on another bus.  Am I
correct ??
 
Thanks
 
Villy
 
 The Answer is:
 
  This is rather far afield from the usual haunts of the OpenVMS Wizard.
 
  All shareable OpenVMS disk devices are generally mapped into controller
  A ("Bus A", as refered to in the question) as there is no way to ensure
  that a particular shared device is on the same controller (bus) on each
  system.  Thus using controller A allows a consistent device name across
  all systems sharing direct access, which thus allows OpenVMS to determine
  that there are multiple paths into the same physical device.
 
  And the usual approach to reference devices in a device-independent
  fashion is to use the DISK$volumelabel logical name, or some other
  similar and site-specific logical name, to refer to the device, and
  completely eliminate anything that even remotely resembles a physical
  device specification.
 
  Serving disks generally requires enabling various settings within
  CLUSTER_CONFIG (or CLUSTER_CONFIG_LAN), as appropriate.  In general,
  you will want to enable all available interconnects.  DSSI, Ethernet,
  CI, etc.  For information, see the above tool, and see the cluster
  documentation available in the OpenVMS documentation set.
 
  The Wizard would always verify the DSSI node settings for the disks
  and for the host(s) before using the configuration.  The Wizard would
  assume that changes are needed until proven overwise, with particular
  attention to the potential for disk device unit number collisions
  within a disk allocation class, and tape device unit number collisions
  within a tape allocation class.
 
  To alter the DSSI unit number within the DSSI ISE, the Wizard would use
  the ISE parameters FORCEUNI to 0, UNITNUM to the desired device unit
  number.  The Wizard would recommend values above 7 here, to avoid any
  possiblity of DSSI address conflicts.  This setting will override the
  default configuration, and allows the disk to be set to a unit number
  value other than the DSSI node ID.
 
  To serve the disks to other nodes, the host ALLOCLASS parameter and
  the ISE value ALLCLASS must be set to the same non-zero allocation class
  value.  This value should be set to the same value on all hosts that
  will be serving the disk(s).  Within a single allocation class, make
  certain that all disk unit numbers are unique.
 
  While resetting FORCEUNI and UNITNUM and ALLCLASS in the ISE, you can
  also reset NODENAME to an aesthetically pleasing sequence of characters.
 
  From the 4000-series console SET HOST command or -- if FYDRIVER is
  configured -- from the DCL SET HOST/HSC command -- one connects out
  to the `PARAMS' application out in the RF ISE, and issues the following
  commands:
 
    Systems with more than one integrated DSSI (eg: VAX 4000-300):
      &gt;&gt;&gt; SET HOST/DUP/DSSI/BUS:[0,1] dssi_node_number PARAMS
 
    Systems with one integrated DSSI (eg: VAX 4000-200, MicroVAX 3300):
      &gt;&gt;&gt; SET HOST/DUP/DSSI dssi_node_number PARAMS
 
    Systems with a KFQSA Q-bus DSSI controller:
      &gt;&gt; SET HOST/DUP/UQSSP port_controller_number PARAMS
                (use SHOW DSSI to get the port_controller_number)
 
        The keyword `PARAMS' on the SET HOST to get to the parameter
	settings.  Use `DIRECT' to get a directory of tools availabile
	`within' the DSSI ISE.
 
        Once in the PARAMS tool:
 
        PARAMS&gt; SET NODENAME nodename   ! max 8 alphanumeric chars (use 6)
        PARAMS&gt; SET UNITNUM n           ! request for specific unit number
        PARAMS&gt; SET ALLCLASS n          ! set to match host allclass
        PARAMS&gt; SET FORCEUNI 0          ! 0=use UNITNUM, 1=use DSSI node
 
        The Wizard would recommend using a maximum of 6 alphanumeric
	characters for the system communications services (SCS) node
	name.
 
  To alter the address of the DSSI host controller, use the host address
  plug.  On those controllers that do not have plugs -- such as the VAX
  4000 model 200, the VAX 3300, and the VAX 3400 -- use the jumper posts
  on the system processor board, usually with bits 1 and 3 labeled.  The
  DSSI address is encoded in octal, with the least significant bit as 3.
 
  The VAX 4000 model 100 has jumper posts on the DSSI adapter, usually
  with bits 4, 2, and 1 labeled.  The DSSI address is encoded in octal,
  with the least significant bit as 1.
 
  The DSSI bus ID of each connection -- host or storage controller -- must
  be unique across all nodes connected to the same DSSI.
 
  When a unit number, system communication services (SCS) node name,
  allocation class, or other similar value changes, the entire cluster
  must typically be rebooted.
 
  Since this is OpenVMS VAX and DSSI, the Wizard will not discuss port
  allocation classes (PACs).  PACs are a feature of OpenVMS Alpha V7.1
  and later, and are intended for use with shared SCSI configurations.
 
