Rack mounted electronic devices come in specific packages that are designed to facilitate their mounting into a machined frame. Many simply refer to this as a server rack. They come in many different shapes and sizes but all allow for units to be installed with in them. Once units are installed into the frame they're usually bolted in place. When considering the size of the frame needed its useful to keep rack units in mind.
What is a Rack Unit?
A single rack unit is 1 34" tall, hence someone wanting to install a 3u rack server package would need a 5 14" rack to install it into. Server farms could easily get confused, especially because these measurements are given in imperial units on most things while manufacturers ship equipment denoted in metric. Fortunately rack units are standard across the board.
Standard Server Measurements
This means no one has to actually do any measurements on his or her own. If someone wants to purchase a server it would simply read some number of rack units, and then the buyer could just as easily go and buy a rack that fits that figure. For instance a 2u server would fit into a 2u rack system. Of course these sizes aren't even necessarily confined to the world of information technology.
Other Uses of Standard Racks
Data centres and professional studios tend to use rack-mounted equipment, and the racks are all standard sizes. That means that equipment can theoretically be mixed and matched. Recording studios and the like use racks just as frequently as server farms do, but those who are trying to bring their studios into the cloud or some other networking system might want to install a server alongside the rest of their equipment. Those who do this should make sure there is sufficient room for each piece of equipment to cool itself.
blade server Option
Multiple server module architecture has allowed numerous devices to be stored in a single chassis. These units are normally called blades and fit together into a frame. That frame is not a substitute for a solid rack mount, however, and it will still be assigned a rack unit number and have to be bolted into the server rack. Blade servers usually have some kind of independently managed administration system. Some of them might include a network switch or storage dongle that can help out individual system administrators.
Unitary Versus Rack Mounted Designs
Anyone trying to pick what kind of equipment they plan to install in their server data centre will invariably come across the question of whether they should install a unitary data system or a 3u rack server unit. Generally unitary stand up server models are the least expensive of the bunch and can be fit into any data centre with a sufficient amount of floor space. On the other hand they aren't nearly as adaptable as rack-mounted solutions. Those who install adjustable frames can go back later and insert more server devices. This makes them a better option for most installations. On top of this they tend to be easier to maintain. Over the long run they might have additional cost benefits over unitary models as well.