This has led to the rise of “server farms”, also known as data centres or web hotels — vast warehouses that provide floorspace, power and network connectivity for large numbers of computers, and which are located predominantly in urban areas. A typical example can be found in Santa Clara, just off California’s Highway 101. It is run by Exodus Communications, a web-hosting firm which has nine server farms in Silicon Valley and another 35 around the world. From the outside, the farm is a deliberately nondescript building. A sophisticated security system, with hand scanners and video cameras, keeps out unauthorised visitors. Inside, the building resembles a jail, rather than a farm: it is packed with row upon row of computers in locked metal cages, their fans whirring and lights flashing. The air is filled with the deafening hum of air-conditioning. There are no windows and few people, and the lights are triggered by motion sensors, keeping unvisited parts of the farm in darkness. Exodus’s customers house their computers inside the metal cages, which are supplied with power and network connections. Most of the world’s biggest websites live in buildings like this; Exodus hosts 49 of the top 100.
As if to emphasise how physical constraints apply even to virtual spaces, server farms are still rented by the good old-fashioned square foot. According to figures published in April by Salomon Smith Barney, worldwide server-farm capacity is growing by 50% annually, and will reach 22m square feet by the end of 2001, despite the demise of the dotcoms. Cage space turns out to have other uses, too: boastful corporate logos hang from many cages, and some firms have posted job advertisements in the hope of poaching technical staff from rivals.
The signs are that the storage of information is going to become even more physically concentrated. One reason is the growth of “managed hosting” where, instead of renting space on a farm for their own servers, firms rent the computing capacity along with the power and network connectivity. In short, they simply hand over their data, and leave running the servers to the hosting company. As a result, there is no longer any need for customers to visit farms, so they need not be located in metropolitan areas, where space is limited and expensive. They can be anywhere, provided enough power and bandwidth are available.
In practice the constraint is power. A single server farm can consume as much power as a small airport, or four large hospitals. As a result, says Jon Feiber of Mohr Davidow Ventures, a venture-capital firm, the logical thing to do is to build out-of-town server farms with their own power stations. Such farms, he suggests, could be very large indeed: perhaps a dozen would be enough for the whole of the United States. Just such a facility, with a 24MW gas-fired power station, is being built just outside London by iXguardian, a British computer-services firm. It will be the largest server farm in Europe.