Name that multi-port SCSI device

Ralph O. Weber ralphoweber at
Tue May 25 21:19:46 PDT 1999

* From the T10 Reflector (t10 at, posted by:
* "Ralph O. Weber" <ralphoweber at>
} 1) How does an event on a port of a "thingy" affect the other ports?  Does
} LU to port mapping modify the behavior?
} For example:  A "thingy" has logical units X, Y, and Z. and ports A B and C.
} LU X is connected to ports A and B.  LU Y is connected to Ports B and C.  LU
} Z is only connected to port C.  If a target reset task management function
} is received by Port A what happens to LUs attached to ports B and C?  What
} does an initiator with a nexus to LU Z through Port C experience?

If anybody remembers that last committee pronouncement on this, it's probably
Gerry Houlder.  Otherwise, I'm sure we can agree (or agree to disagree) on
a new answer at a future meeting.

} 2) If an initiator needs to identify the same LU regardless of service
} deliver port, how is this done?

Via a world wide name identifier found in the Device Identifier VPD page.

} 3) If a "thingy" needs to be able to identify the same initiator attached to
} multiple "thingy" ports, how is this done?

No SCSI standard is allowed to place a requirement on "thingies" that would
result in the need for a "thingy" to do this.

} 4) If a target "thingy" needs to identify an initiator "thingy" regardless
} of initiator or target ports how is it done? 

No SCSI standard is allowed to place a requirement on "thingies" that would
result in the need for a "thingy" to do this.

} 5) Does a target "thingy" do something different for multiple nexuses from
} the same initiator "thingy" versus nexuses from different initiators.  Is
} anything different done if multiple initiator "thingy" ports are attached to
} the same target port?

In short, no.  The way a SCSI Device Server is specified to operation is
in relationship to the Initiator that sent the command (or, in the case
of reservations, in relationship to all Initiators except the one that
sent the command).  The initiator is tied to the one and only port that
the target can detect as the source address for the command.  If multiple
ports can pass commands for a single application client, the application
client and only the application client is responsible for coordinating
any activities that need to be coordinated.  Such responsibilities never
fall on the target or device server.

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