[c-nsp] Few questions regarding fixed vs modular and when which is better.

[Seth Mattinen]

James Slepicka wrote:
> This is more or less what I do as well and I'm pretty happy with it. 
> Cabinets have 48-port patch panels tied over to a relay rack.  In one
> cabinet, the first half of the ports go to switch A, the other half to
> switch B.   Same thing in the second cabinet, except A/B are reversed,
> so each pair of cabinets shares a pair of switches.  It's effectively a
> top-of-rack design, except that the switches are located at the end of
> the row.  See http://slepicka.net/physicaldesign.png to get an idea of
> what I'm talking about.  Access layer switches are 4948-10GEs w/ dual
> power supplies connected to 6506s w/ 6704-10GEs in the distribution layer.
> 
> The biggest benefit of this config is that cable management is a snap
> and it's really easy to replace a switch if you need to.  Instead of
> messing around with a switch and a ton of cables at the top of the
> cabinet, I only need to move around a bunch of 1 foot cables in the
> rack.  I suppose the same thing could be done in the cabinet at the
> expense of additional space.  A ports are always the primary, and B's
> are backup.  With a 10Gb link to the distribution layer, that means I'm
> running at about 2.4:1 oversubscription assuming everything is happy. 
> Downsides are that cabling can be expensive (all that CAT-6 vs. some
> fiber) and that it's tough for the server guys to figure out what
> switch/port they're plugging into at times.
> 
> I do hope that Cisco doesn't EOL the 4948-10GE without releasing a
> switch with similar features in a 1U form factor.
> 

I do the same thing (patch panels to switch racks) but for a different
reason: routers and switches frequently have incompatible airflow
compared to front-to-back rack mount servers. This way, I can keep all
my server racks as front-to-back airflow and the side vent,
back-to-front vent (even passive cooling) routing/switching/monitoring
gear have their own special area.

-- 
Seth Mattinen		sethm at rollernet.us
Roller Network LLC