Re: Symmetric vs Asymmetric

["Matt Wakeley" <matt_wakeley@agilent.com>]

"VonStamwitz, Paul" wrote:

> In general I agree with the asymmetric model.
>
> David Robinson wrote:
> >
> > That's not a bug, that's a feature! Having the asymmetric degenerate
> > into symmetric with just one connection is a good thing.  For starters
> > it is easier to implement initially or in cheap devices and doesn't
> > have the baggage that a true symmetric design would require
> > but is not needed with one connection. I would oppose mandating
> > two connections minimum, if flow control is a problem then the defacto
> > configuration will be two connections, but lets not require it.
> >
>
> I agree with David. I oppose a two connection minimum.

I disagree. Initial implementations and cheap hardware will have the iSCSI
implementation in software.  It is easy to do anything in software - open a
thousand connections, perhaps hundreds of thousands, one per each LU, it
doesn't care - it just uses up more memory.

However, for the high performance implementations that will implement iSCSI in
hardware, doing a function one way sometimes, and another other times, will
require more hardware and more testing (by both the hardware vendors and the
value add vendors) to test both functions.

One connection per LU also has the huge issue of requiring lots of on-hardware
resources and memory to maintain the hundreds or thousands of connections that
will be required.... and you want a cost competitive solution?

> > Personally I would still prefer one connection per LUN, but the
> > proposed asymmetric model is a good compromise. You could
> > still deploy an implementation with a connection per LUN and not
> > have any significant unnecessary baggage. Not true of the symmetric
> > model.
> >
>
> One connection per LUN alleviates commands being flow controlled by large
> transfers of data.

Exactly.

>
>
> Paul

-Matt