Re: iSCSI : On the subject of R2T and Task Tags.

[Santosh Rao <santoshr@cup.hp.com>]

When multiple R2Ts are outstanding, the targets need a tag per R2T to track their
SCSI State Table Entries for each R2T. While its usage depends on how each
individual programming model implements this feature, I believe the header should
provide support to track each R2T using an id that the target can lookup for its
R2T data buffer pointers.

Not having this id will cause a more expensive lookup that needs to be based on the
Buffer Offset that the WRITE Data PDUs will carry.

Implementations can choose to not use (0xFFFF) or use a single value for the Target
R2T Tag if they do not need this feature or specify MaxOutstandingR2T as 1.

- Santosh Rao


Raghavendra Rao wrote:

> > The "Target Transfer Tag" that you are referring to is per R2T and not per
> task.
> > There is no per-task identifier that can be used by the targets to track the
> > task. They will either have to :
>
> I don't think per R2T target tag makes sense.
>
> It would simplify if target maintains one-to-one mapping of target and initiator
> task tags. So, until the task is terminated, the target should simply post the
> same target task identifier in every R2T it transmits corresponding to an
> initiator task tag.
>
> -JP
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