Report LUNs command and SCC

George Penokie GOP at rchvmp3.vnet.ibm.COM
Fri Apr 26 12:57:56 PDT 1996


* From the SCSI Reflector, posted by:
* "George Penokie" <GOP at RCHVMP3.VNET.IBM.COM>
*
Ron writes,
> As an initiator we have a need to determine the known logical units
> in an SCC device.  If a REPORT LUNS command is sent to an SCC device
> what should it return?  Could the SCC device report the LUNs associated
> with all of the addressing methods (volume set, peripheral device, logical
> unit, base address)?

The answer is Yes.  When a REPORT LUNs command is sent to the base address
(LUN 0) of a SCC device the SCC should report all directly addressable
LUNs it knows about.(Volume sets, and peripheral devices; note those are
the only two types of objects that can be directly addressed.)

Also, don't confuse addressing methods (which are part of the LUN) with
the LUN.  Addressing method is a field within the 8 byte LUN structure.

Now you might say all that is fine but what if the protocol I am using
does not support the 2 byte LUN addressing??  For example parallel SCSI
only supports 6 bits of LUN addressability.

My answer to that is Opps!!!!  The only way to find out those LUN addresses
is the old SCSI way of issuing identify commands to the LUN to see if it
is there.  Sence that is no good I will propose the SCC-2 activity (which is
just starting up) add a new address mode of protocol specific (11b).  Then
it would be up to the specific protocol to define the address method specific
field of the xx level addressing field of the 8 byte LUN structure.  Which
in the case of parallel would be added to the defination in annex a of SCC.

If you have any questions about this let me know.

Bye for now,
George Penokie




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