Learn what a rack cabinet is and what models you can buy

Many of you have seen in the Data Processing Centers (DPCs), small and medium-sized companies, and even offices, metal cabinets that have the main computer systems and communications networks. These cabinets are called computer cabinets or racks, and they are the way to safely store all the equipment in companies, and correctly order all the wiring in case an intervention needs to be carried out on it. Today in RedesZone we are going to explain what a rack cabinet is, what they are for, how much they measure and what models exist.

What is a rack or frame cabinet?

A rack is a cabinet with a metal base and structure, the main objective of which is to house all the computer and telecommunications systems that the companies or organizations where they are installed need. In these rack cabinets is where the servers, switches, professional routers, NAS servers, DAS, uninterruptible power supplies (UPS) and, of course, all the network cabling will be stored to provide the different services to the local network.

Currently, any company that has a minimum of equipment connected via cable will have a switch with 24 or more ports, a professional rackable switch that must go in one of these cabinets. The same happens if we have a server, if we have a server or tower-type NAS, you can also put it in the rack with fixed or mobile trays, if we have a rack-type server (which are generally somewhat more expensive), we will save a lot of space inside the rack because they will only occupy 1U or 2U.

In rack cabinets, all dimensions are always standardized, with the aim that any equipment that we are going to install (switches, routers, NAS servers, UPS) are compatible and we do not have any problems. These cabinets have removable sides, to easily access the sides of the equipment that we install, in addition, we can buy them with glass doors (on the front) to see very well what is inside without having to open the door, or we will also have perforated metal doors to facilitate air flow and adequately cool the equipment inside. Finally, we also have the possibility of having cabinets with two doors, this is ideal so that they occupy half the space when they are opened and placed in places where there is not too much space, such as in small rooms, corridors etc.

Dimensions of a rack or rack


Regarding the dimensions of the racks, the first thing that we must take into account is the height, which is measured in a unit called U. This «U» equals 1.75 inches, or 44.45mm. All equipment such as routers or switches must always have a height of 4.4 cm high, to be exactly the same as a U and to be able to rack the equipment without any problem. In the case of servers, they usually occupy 2U and even more, but it will always be measured in multiples of a U to find its height. In this way, we can find racks that have a height of 22U, 42U or more, depending on the model we are looking at.

The height in U never corresponds to the real height of the cabinet itself, because the U only indicate the effective height for the installation of the equipment, not to mention that the cabinets usually have wheels, and in the upper part a fan system to extract hot air from inside. For example, the most normal thing is that a 42U cabinet measures a little more than 2 meters (instead of 1.86 meters that it should measure based on the U).


Regarding the width, normally the racks are always 19 inches (48.26cm wide) which are actually 600mm wide on the outside, because we will always have space for the lateral wiring and the “walls” of the cabinet itself. There are also 800mm wide racks, but these are still 19-inch racks, this allows us to add 10cm to each side to greatly facilitate the management of the network cabling that is going to be used, we will have it much easier to pass all the cabling network or fiber to interconnect the different equipment.


Finally, regarding the depth of the cabinets, they usually range from 600mm deep to 1,200mm deep. Depending on which servers or equipment we are going to install, we will need a larger fund or a smaller fund. For this reason, before buying a rack it is advisable to see the size of the servers that we already have purchased, because it is possible that they will not fit us if we have a cabinet with little depth. As a general recommendation, the equipment with the deepest depth should be about 15cm smaller than the rack that we are going to buy, to facilitate the management of the cables (power, data, etc.), that is, there always has to “spare” space inside the rack to not have problems when it comes to managing the wiring.

What are they for?

A rack cabinet is used to have all the network equipment and main computer systems (mainly servers) in the same place and very well organized. If we have all the computer systems in a rack cabinet, we can carry out interventions more easily, interconnect networks and even expand the infrastructure we already have. Another strong point of the racks is that it will allow us to adequately ventilate all the equipment, most cabinets have fans in the upper part to expel the hot air that is generated inside, in addition, they also usually have in their front and back Perforated doors to facilitate the passage of cold air to the rack and the exit of hot air.

In order to have a good temperature management, in any good data center, we will always have a cold air corridor where there will be air conditioning to cool the equipment inside the rack, and a hot air corridor where the rack and the servers will expel the hot air.

Types of rack cabinets

We mainly have two types of rack cabinets, floor models and wall models. Depending on our needs and budget, we can choose one type of wardrobe or another. It is also very important to know where we are going to place the closet, because wall-type cabinets are much smaller than floor-standing ones. In addition, we must take into account the accessories that we have for the racks, in order to facilitate the installation and management of all the cabling.

Wall rack

This type of cabinets allows us to place them on a table or directly on the wall, as a shelf. If we need a cabinet to install a switch and a router only, it is a very good option because it has a very low price, and it is ideal for training centers, schools where they do not need too much connectivity, domestic homes etc. These types of cabinets are a “mini” version of floor racks, but they are still perfectly valid because they comply with all standard dimensions. Of course, these types of cabinets can also be placed on the floor, but they do not have wheels like floor cabinets, so it is most normal to have them on the wall or on a table.

These types of cabinets usually have few U, about 6U approximately, because they usually have a load limit of about 50-70Kg approximately. This type of cabinets also have removable sides, cooling in the upper part of the rack, a door with glass and a key, and we can even properly manage the wiring within it. We must take into account the limitations of this type of cabinets: we have few U units available to install equipment, and if one is not rackable (it is a tower type) you will have even less space, so you should evaluate it carefully.

9U wall-mounted rack cabinet



Floor racks

This type of cabinets are specifically designed to have them directly on the floor, they have lockable wheels to move it easily and quickly, we will not need to anchor it to the wall, it is placed directly on the floor and the wheels are locked to prevent its movement. If we need a closet to install a router, several switches and servers, this is the option you need because it will give you the greatest space in height. These types of cabinets are aimed at small and medium-sized companies where we have more computer equipment to store.

The floor racks can be disassembled on all sides (including the door), the front door can be chosen in glass or perforated, and it is the one that will provide the most space, because the height and width limit is set by the location where we go. to place it. Normally the depth dimensions of these cabinets range from 600mm to 1,200mm, in addition, in width we also have the possibility of buying 600mm or 800mm, the latter is ideal for very good management of all network and fiber cabling that go to the different teams.

22U floor rack



Accessories that a rack can have

When we buy a rack cabinet, they usually come with a few minimum accessories for the correct installation of the different computer systems, however, you may need to additionally buy other quite interesting accessories that we detail below.

Fixed or sliding trays

Normally, most of the equipment that we install in a rack cabinet is “rackable”, however, it is possible that we have a UPS or a NAS server in tower format, and therefore, we cannot install it properly. In order to install this type of equipment, and even to put a monitor and keyboard inside the rack itself to carry out interventions locally, the use of trays is necessary. These trays are metal structures that are installed on the sides of the rack, and that support a server, a monitor or any other computing device.

There are a total of three types of trays:

  • Fixed trays : they have a fixed bottom, the width is the default 19 ”width of the cabinets. Once you install them they cannot be moved, neither forward, backward or to one side or to the other, they are completely fixed and on top you can place the equipment.
Fixed rack tray



  • Fixed trays adjustable in depth : they have a variable depth, depending on our rack (600mm or 800mm) we can put them with more depth or less depth. They are an alternative to fixed trays to adapt to different cabinet depths.
Adjustable fixed tray



  • Sliding trays : these types of trays are installed in a fixed way, but later they can be moved towards the rack door to facilitate the installation or management of the computer systems that you have placed.
Sliding tray



Blind panel

This panel will allow us to “cover” one or more U of the rack, in such a way that internally we have a “hole”. This is what it does is to cover the unused spaces, and the reason for not using these U that we have available in the cabinet is to cover the wiring that is between the cabinet, and also to improve the cooling of the components, leaving « empty spaces »internally.

Blank panel rack



As you can see, it is a completely black panel that covers everything behind the rack, in this way, if we see the rack from the front, we can see a certain order.

Cable Guides – Cable Distribution Rings

This accessory is essential if you want to have organized the cables inside the rack, it will allow us to easily pass the different network and fiber cables to have the best possible order. We must bear in mind that within a rack we will have a large amount of cabling, both network and fiber cables, that go to the different switches, routers, patch panels, etc.

Cable guides



There are several types of cable guides, if we are going to pass many cables the previous one is ideal, but we can also buy cable glands with a brush if we are not going to have too much wiring and we want to hide it.

Cable gland with brush

The cable glands with a brush are like a blank panel, but in the central part we have it open with a brush to pass the cables through there so that they do not move. The cable glands with a brush will allow us to pass the cables from the front of the cabinet to the rear, and all this while hiding all the cables behind this brush.

Cable gland with brush



Patch panel

A patch panel is one of the most necessary accessories in a rack cabinet, the network cabling comes from the outside and is directly put into the patch panel, to later take short network cables (patch cords) to the switch or the different equipment in this way, we will be able to document the entire installation with the wiring very well. We must bear in mind that today there are Cat5e patch panels and also Cat 6, the latter being the most recommended.

Patch panel



The patch panels usually occupy 1U, and will allow us to order the wiring that comes from the outside.

Power strips

Power strips are another essential accessory in a rack cabinet, in fact, normally when you buy one, it already comes with one or more built-in strips to power all the equipment. The rules for the cabinets are normal strips but adapted specifically for placement in the rack with the typical hardware of the cabinets, below, you can see it:

Rack cabinet power strip



The most normal thing is to have one or two power strips in the closet, but it will depend on how many equipment you are going to connect simultaneously, of course.

Ventilation units

The ventilation in a rack cabinet is essential, we must bear in mind that the heat always rises, therefore, we have a ventilation unit to catch the hot air from inside and expel it outside is something very important. Additional ventilation units can also be placed inside the cabinet, either with 2 or with 4 fans. We must also bear in mind that there are ventilation units with a built-in thermostat, which will mark the temperature inside the closet.

Rack ventilation unit




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