An interesting article was published few days ago on The Register by Timothy Prickett Morgan, talking on the traditional three-tier networks versus flat networks. While the topic is not new, it seems that more datacenter networks now adopt the high-performance architectures and go flat.
The three-tier network is the traditional hierarchical datacenter network and it was never fast enough, nor cost effective enough, but was championed by Cisco and therefore used in many places. The HPC side of the world went for the flat networks, which delivers lower latency, higher utilization and of course, is much more cost effective. Many of the new “web 2.0” applications today adopt the HPC concepts of parallelism and suffer from low performance in the three-tier network. Going to flat network is the ideal situation for them.
It was funny the read that Blade Network (now IBM) agrees that the datacenter application are going the HPC way, but their company vision is to continue with the three-tier concept… well… in my eyes this is the right decision if you want to stay behind… Flat network, such as CLOS network, is the better way for any large scale system, both for performance and for cost.