|Data Centre tourist view|
The aisles of servers and network equipment you see above looks quite different to a normal office. Those dense racks may be powering Google searches, or storing billions of facebook pages or running some corporate intranet, but the fundamental design principles are just the same.
|Data Centre architecture for web services|
Most sufficiently-large networks are three-tier constructions. In the centre is a high-speed backbone - the core network - which is optimised for high-throughput of data packets and connects to the outside world: the Internet, other corporate sites, the Extranet.
Attached to the high-speed core is an aggregation layer. This concentrates the traffic from large numbers of smaller local area networks and provides a home for network services such as: firewalls, security systems (ID&P), monitoring systems, caches, SSL accelerators, load balancers and the like.
Finally we have the access layer: switches which directly connect to those masses of servers and provide their primary network connectivity. In a smaller network, the access and aggregation layers may be merged.
In a certain sense, the essence of data centre design comes down to the architecture diagram shown above.