When we needs to upgrade an existing installation or buy new server we have main 3 choices: Rack , Blade and Tower Server.
If you have data center of any reasonable size, you probably choose will be rack server. This type servers are generally more expensive than other servers, have a lot storage capacity. they are for medium-sized businesses or micro-businesses, and small businesses for which information technology is a strategic priority. Rack servers are measured in rack units or “U’s” and range from 1U to 5U, 8U, and more. The benefit of this type of server is that having all components of the system located in the same place makes it easier to manage.
Rack servers are very expandable and some include more than 10 disks right in the chassis and support more than 4 processors, each with multiple cores. Many rack servers support large amounts of RAM.
This type of server looks alike a desktop computer. But tower server very powerful and have bundled software tools to manage them. If you planned to buy many server probably you will not choice this type of server . Because these server require more space than blade or rack server.
These servers are an additional level of innovation on top of Rack Servers. Blade servers will give you much greater processing power, take up less space and use less energy than other forms of server used for the same purposes. Unlike a rack-mount server, a blade server needs a blade enclosure. A blade enclosure, which can hold multiple blade servers, provides services such as power, cooling, networking, various interconnects and management. Together, blades and the blade enclosure form a blade system. Blade servers are also more expensive than the other two types of server.