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

[Raghavendra Rao <jp.raghavendra@sun.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.
> 

If a target is doing the I/O in a lot of bits-n-pieces with several R2Ts,
it must already be spending a lot of cycles to complete the I/Os - And
I can't believe a lookup (if it needs to) is going to be excessively
harmful compared to the magnitude of processing it must already be doing
(in getting buffers available in piecemeal, allocating, building, and
transmiting R2T for each such buffer and tracking the I/O progress).

Let us also not overlook the link bandwidth utilization of such examples
of doing I/Os. Please explain what is the gain in improving a bad transfer
example ?

-JP