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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iscsi : changes involving tgt portal group tag.Apologies for the late followup, but this discussion has me puzzled. Part of the concern appears to be around the worry that an initiator might reconnect to "the wrong" port and as a result end up talking to the wrong LU when it issues additional commands to a LUN it knows. I don't understand how that's possible. SAM-2 section 4.7.3 shows that an LU is a component of a Device (not of a Port). And 4.8 says that a LUN "identifies the logical unit within a SCSI target device". In other words, no matter what port you use to access a device, a given LUN identifies the same LU in that device. As for the rule in SAM-2 section 4.7.7 that a "port name shall never change" and the conclusion that therefore a TPGT must be persistent, I would ask "across what scope?" and "how would you tell"? If I have an iSCSI device that at time T has a port named X, and at time T+1 has a port named Y, how would I test whether the proposed requirement has been implemented? I think the answer is: if you can see state you created, such as reservation state, but it's now attached to a different port name, then that requirement has been violated. Conversely, whenever a target port has no state it needs to remember (no reservations, no initiator-specific mode pages (iSCSI section 2.4.3.1)) then it can disappear and a new target port can appear in its place -- or equivalently, the port can simply change its name, you can't tell the difference. I guess what I'm getting at is this: a requirement for something to be persistent has meaning only if there's state attached to that persistent thing, state that you can observe. What exactly is that state and long must it be kept? iSCSI 2.4.3.1 lists some (but it says "e.g." so there might be other state?). Without a complete list of that state it's hard to figure out what the correct rule should be. paul
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