[c-nsp] Splitting root bridges (was Migration to Rapid-PVST)

[Joe Maimon]

Matt Stockdale wrote:

> I've seen the concept of splitting your roots across your 2 core
> switches like this mentioned before, but something about this
> conventional wisdom escapes me - 
> 
>   If your goal for this setup (2 routers, 2 core switches, 2
> distribution switches, N access switches) is redundancy instead of
> performance, does it make sense to split the load like this? Isn't it
> possible to reach > 50% load on both sides, such that were one half to
> fail, the remaining portion couldn't pick up the slack?

In these cases people are typically willing to endure degraded service 
during outages, for some definition of degraded, in return for a greater 
ROI on equipment purchased during non-outages.

See RAID5 v. RAID1