Blade servers are a type of computer used in web hosting data centres as a means of:

1. fitting more computers into small space.
2. reducing the amount of infrastructure required to service each computer in a rack.

Traditionally, web servers have been 19" wide and 1.75" tall (See 1U) and have fitted in to a rack contain 42 of these computers, each server having its own power supply and network connection. The picture below shows a traditional 1U rack server.

In a blade system, there is an enclosure which deals with the network connection and power connection. It usually takes the space of 3 traditional 1U rack servers, but can store up to 8 blade servers.

Each individual blade is placed vertically within the enclosure. The picture on the left shows two enclosures, each holding 8 blades. One of the blades is highlighted in red.While space is saved and more computing power can be placed in a smaller space, blade servers do not have storage, so separate storage servers also have to be included in the set up.

This photograph shows an individual IBM HS20 blade server.