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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iscsi : DataPDULength can differ in each direction.Julian, > Implementation specific? I assume you wanted to say connection specific. No, I said what I meant and I meant what I said. :-) I can easily envision implementation restrictions (bounds if you will) with regard to any of the parameters I listed. I think you are being far too optimistic that implementors will enable all that the spec allows. In particular: > Following this same line of reasoning the keys: > > MaxBurstSize > FirstBurstSize An implementation can easily be limited by the size of burst it can handle due to buffering capacity or other data structure limitations of the HW. > MaxOutstandingR2T This requires resources in the HW implementation to track the outstanding requests. Implementations will vary in the capacity of tracking said requests. > DataPDUInOrder > DataSequenceInOrder Some HW implementations will limited in their capability to handle out of order data. Current Fibre Channel implementations illustrate this type of constraint well. > ErrorRecoveryLevel Implementations may limit the types of error recovery available. I can envision different implementation choices being made in the ability to restart IOs. I also think it may be problematic moving and restarting an IO between implementations. > No the parameters you quote (except MaxOutstandingR2T) are not connection > specific. > They reflect multiplexing capability that the transport allows for SCSI. > Making them connection specific will > only complicate things with no added benefit. In which case you add the complication that the iSCSI layer will have to query (or know apriori) the capabilities of all its interfaces prior to opening any leading connections. That way it won't negotiate beyond the capabilities of any of its individual interfaces. Dave
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