In some situations, the type of server hardware you use is the least of your concerns, but if you are setting up your own data center, you will need to decide which type of server you prefer. The three main types of servers are: towers, racks, and blades.
Towers – You probably recognize towers, as they look very similar to desktop PCs. If space is not a concern, you can usually get more drives and more hardware into a single tower. If you need scalability, however, space can become a real concern.
Rack Servers – Racks are designed to hold multiple servers, and rack servers are specially constructed to fit in these small spaces. They are essentially stacked right on top of each other, which does make cooling more difficult, while scaling is much easier.
Blade Servers – Although they are very similar to rack servers in design, some components have been removed from blade servers and are instead shared among multiple ones. This makes blade servers even thinner, but also more expensive.
Ultimately, the type of server you choose depends on your needs. If space is your main concern, you may opt for racks. If cooling will be a problem but not space, you may choose towers. If money is not a problem and you need space and consolidation, blades are the way to go.