Cisco Nexus

Tue Feb 3 01:03:06 UTC 2015

> Brandon Ewing <nicotine at warningg.com> wrote:
> 
>> David Bass wrote:
>> The n2k ToR is not a great design for user or storage interfaces if most of your traffic is east/west.  It is great as a low cost ilo/drac/choose your oob port, or if most of your traffic is north/south.  Biggest thing to remember is that it is not a switch, and has limitations such as not connecting other switches to it. Like anything else you have to understand the product so that you don't engineer something that it wasn't designed to do.
> 
> And remember -- The Nexus 2K performs absolutely ZERO local switching -- all
> frames received from client ports are just copied to the upstream device, so
> it can handle the frame/packet forwarding logic.                                 

What this really does is force you to consider how much of your East-West is rack-local, versus off rack.

Rack-local-heavy hurts as badly as off rack, with FEX.

If you want to / can localize E/W tighter than that then you want real TOR switching.  If the average E-W is cross rack then the FEX are performance equivalent.  For random distributions this comes at a few racks.  For intentional distributions it's probably better to TOR switch from day one.

George William Herbert
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