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

From: "Julian Satran" <[email-masked]>
Date: Tue, 13 Nov 2001 10:34:33 +0200

Paul,

I would appreciate if you could expand on what your concern about the 
fastpath is.
And I would appreciate also you telling us what sufficient refers to.

As for NO (uppercase "n" and "o") I do not find it in any "common acronym" 
list so I assume it is a way (impolite) of saying "we should not consider" 
it.

Julo

Paul Koning <[email-masked]>
12-11-01 19:02
Please respond to Paul Koning

        To:     Julian Satran/Haifa/IBM@IBMIL
        cc:     [email-masked]
        Subject:        Re: iSCSI - change proposal LUN field definition on every PDU

Excerpt of message (sent 12 November 2001) by Julian Satran:
> 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).

NO.

I can see no good reason to add work to an implementation fastpath for
this.  It slightly simplifies instrumentation, but instrumentation is
certainly possible without it.  That is sufficient.

       paul

---

From: Paul Koning <[email-masked]>
Date: Tue, 13 Nov 2001 10:09:47 -0500

> I would appreciate if you could expand on what your concern about the 

"fastpath" is a commonly used term to describe the performance
critical parts of an implementation -- typically a software
implementation. 

In designing a fastpath, a major consideration is the avoidance of
*any* extra operations not strictly necessary for successful operation
of the protocol in question.

Supplying LUNs for monitoring devices is not needed for successful
communication between initiator and target, and it consumes additional
cycles.  Not many, admittedly.  But in fastpath design, you don't want
to accept unnecessary overhead just because it's "not much".

> And I would appreciate also you telling us what sufficient refers to.

"sufficient" refers to the current design.  Instrumentation can figure
out what LUN each message relates to.  It requires state to do so, but
that is not a problem.

> list so I assume it is a way (impolite) of saying "we should not consider" 

Capitalizing a word is a common way to indicate emphasis, which is
what I intended.  It is not, as far as I know, a common way to
indicate impoliteness, and indeed I did not intend any.

	 paul