Problems with Dual Port SCSI

Charles Monia, SHR3-2/W3, 237-6757 05-Aug-1994 1613 monia at starch.enet.dec.com
Fri Aug 5 13:11:27 PDT 1994


HI:

In adapting the dual port changes to SAM, I've run into a problem with
information returned by the PORT STATUS command specified in 93-041R2.

According to the specification, the RID field returned at byte
offset 2 is supposed to contain the initiator identifier for the device
which has reserved the logical unit. There are two problems. First,
the I/D field is too small for all protocols, aside from SIP. Secondly, for some
protocols, like SBP, the initiator I/D is assigned by the target device at
login and thus is useless to another device.

I'm told that the intent of this parameter is to allow the inquiring device to 
communicate with the holder of the reservation. In that case, it seems like
this field ought to contain the reserver's target address or something
that can be translated to a target address. As matters now stand,
this field is only useful to SIP.

I believe I can work around this problem in SAM. My concern is that, unless
this issue is addressed, the dual-port stuff will be of no use other than for
SIP implementations. In that case, the additions in  SAM to generalize
the dual-porting concept will have resulted in increased complexity to no 
purpose.


Suggestions?


Charles.






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