FCP-2 resource recovery question

Howard Green green at prisa.com
Thu Jul 15 20:40:01 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* "Howard Green" <green at prisa.com>
*
I've got a question regarding target resource recovery. FCP-2, in section
10.3 on RR_TOV, specifies that a target can recover resources in use on
behalf of an initiator if the initiator fails to authenticate itself within
RR_TOV following completion of loop initialization.

The FCP-2 text (and the corresponding FC-TAPE text, too) is pretty close to
a verbatim inclusion from PLDA, which dealt with FibreChannel universes no
larger than a single loop. In such an environment, one could reasonably
expect the demise of an initiator to cause a loop initialization, which
would provide targets with the event needed to trigger RR_TOV action, and
ultimately, resource recovery.

Times have changed, though, and Fabrics are a reality, and therein lies my
question. In a Fabric environment, initiator and target may be on different
Fabric ports---i.e., not on the same loop---and an initialization on one
loop won't generally propagate to any other. Further, if either initiator or
target is attached to the Fabric via a link, loop initialization events are,
um, kind of problematic.

So, suppose an initiator on one Fabric port is using a target on another. If
the initiator kicks the bucket, what event serves to inform the target that
it ought to start its resource recovery process?

One (obvious?) solution is to require targets to register for and monitor
RSCNs (and indeed, there are targets that already do this). If a target
receives an RSCN that pertains to a logged-in initiator, it suspends that
initiator (and presumably only that initiator!) and starts its RR_TOV timer.

Am I missing something? It seems like there's got to be something more than
loop initialization to trigger resource recovery in a Fabric environment.


Howard Green
Prisa Networks



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