[openib-general] ibstatus support for speed

[Michael Krause]

At 02:43 PM 10/30/2006, Hal Rosenstock wrote:
>On Mon, 2006-10-30 at 17:29, Michael Krause wrote:
> > At 02:05 PM 10/30/2006, Roland Dreier wrote:
> > >     Hal> So rate = speed * width ?
> > >
> > >Yes, you should see the right think on DDR systems etc.
> >
> > Strange.  Bandwidth = signaling rate * width.   This of course is raw
> > bandwidth prior to encoding, protocol, etc. overheads which will derate 
> the
> > effective application bandwidth minimally be 20-25%.
>
>Yes of course. It's just a simple diagnostic to display the width and
>speed simply.
>
> > If the goal is
> > provide a true indication of the maximum peak bandwidth that an 
> application
> > might see,
>
>That's not the goal of this simplistic tool.
>
> >  then stating 10 Gbps for an IB x4 SDR is clearly a
> > misrepresentation and out of alignment with other networking links such as
> > Ethernet which customers understand its bandwidth to be minimally after 
> the
> > encoding, etc. is removed from the equation.   The perpetual trend by
> > marketing to use 10 Gbps IB as equivalent to 10 Gbps of application 
> data is
> > actually detrimental not beneficial when it comes to customers.  It
> > inevitably leads to the question of why the application is not achieving
> > the stated bandwidth, i.e. why it is say 700-800MB/s theoretical peak 
> for a
> > x4 while a 10 GbE is 1 GB/s peak.  So much marketing hype has gone forward
> > already.   I realize I'm tilting at windmills but if you are to provide a
> > tool that is supposed to project the maximum bandwidth possible and given
> > the goal of OFA is to provide as much conceptual commonality with existing
> > network stacks / links, then it would be beneficial to have this move
> > towards a much more apple-to-apple communication of information.  I 
> know it
> > would certainly help with having to repeatedly explain why IB 10 Gbps is
> > not the same as 10 GbE to customers and analysts.
>
>Agreed but this is a different issue from what the tool is for.

Understood.


>IMO this issue largely started when IB decided to use the signalling
>rate rather than the data rate like most other networks.

Blame it on marketroids who were more concerned about their naive attempt 
to look better than other technology and not about customers or the people 
who have to continually explain how their drivel is simply 
wrong.  Unfortunately, these same marketroids continual to perpetuate this 
message even now with their apple-to-orange comparisons.  Annoys customers 
who when educated end up with a slightly less favorable opinion of the 
technology.

Mike