Name that multi-port SCSI device

briandm at excite.com briandm at excite.com
Thu May 27 09:50:27 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* briandm at excite.com
*

George

Thanks,
I think I've figured out what I'm missing.  See below.
Please let me know if I've got it wrong.

On Thu, 27 May 1999 00:10:43 -0400, George M. Ericson wrote:
> 
> Given: Port A and B attached to Target with LU X.  Initiator I attached
> to both port A and B. Initiator J attached only to port B.
> 
Using your nomenclature of Tab signifying target with ports A and B (I hope
I'm using it correctly), I believe you would refer to this example as:
Tab(X) 

I consider this example to be similar to what I was describing but you
referred to my example to be something like:
Ta(X) Tb(X)
or:
Ta(Xb) Tb(Xa)

I think I understand why now.  It's the complicating factor of not all LUs
being accessible through all ports.  If I toss in LU Y only accessible
through port B,  your example would become two targets:
Ta(X) Tb(Xa,Y)

My viewpoint is that there are one or more LUs associated with only one
target.  The target may have multiple ports.  The target optionally may be
configured (outside of the standards) to allow an individual LU to be
accessed or not accessed through a particular port.  If you'll allow me to
mangle your notation I view the modified example as Tab(Xab,Yb).
    
I believe your decomposition of my original example specifies the example as
being LUs, *each associated with one or more targets*, each target having
one port.  A target is defined as a set of accessible LUs.

I think we have a disagreement over how to view the mapping of LUs to
ports.
Although I too liked the earlier SAM-2 rev. multi-port section, it didn't
address this issue. 



Brian





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