Re: iSCSI - change proposal LUN field definition on every PDU

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

Julian,

Can you explain further the extent of PDUs that are intended to be
affected by this change ? Also, can you clarify why it is not a problem
for other SCSI transport protocols like FC where the LUN field is not
included in every FC IU ?

IMO, the LUN knowledge is best kept out of the SCSI transport as far as
possible. All LUN level logging/tracing belongs to the SCSI ULP, which
is given a LUN context on each call made to it from the LLP.

At the SCSI LLP layer, tracing/logging as well as state information
should be at the I-T nexus level (session).

I don't (yet) see a sufficient justification for this change. Perhaps,
more information on the motivation for this request may change that.

- Santosh



Julian Satran wrote:
> 
> Dear colleagues,
> 
> A colleague interested in instrumentation approached me with a question
> about stateless logging of specific LU activity.
> With the current iSCSI PDU formats this is not possible.
> We have consistently avoided having fields that are redundant and will
> need consistency checking.
> However I think we should consider including the LU field in all PDUs that
> are referencing a specific LU to simplify this type of instrumentation (as
> we did with the direction bit in the op-code).
> 
> As I am already in "count-down" mode for version 09 I would appreciate
> your comments ASAP.
> 
> Julo

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Santosh Rao
Software Design Engineer,
HP-UX iSCSI Driver Team,
Hewlett Packard, Cupertino.
email : santoshr@cup.hp.com
Phone : 408-447-3751
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