Considerations when selecting a rack by height: In selecting the height of your server rack, you will want to keep in mind both what the cabinet's external height is, and how many "U's" (rack units) of rack mountable equipment you need to fit in it. 1U (One Rack Unit) equals 1.75" in mounting rail height.
Considerations when selecting a rack by depth: In selecting the depth of your server rack you will want to keep in mind the deepest piece of equipment you will be putting in the rack; and then add a couple additional inches for space to run your cables and power cords. Also, please keep in mind that the usable rack depth "rail-to-rail" is typically 1 3/4" less then the actual rack depth.
After you select the Rack Height you need above, you will then be able to select your Server Rack Depth and Server Rack Manufacturer, and configure your rack to your specific requirements.
External Height: Determining the correct rack height is extremely important. Not only should you consider both your current and future internal rack space requirements, but please be sure to allow enough room for ceiling clearance and any cabling or site requirements, as well as any dock or freight elevator limitations you may have.
Rack Units: With the exception of some legacy equipment, monitors, and keyboards, most server and network equipment sold today is intended to be rack mounted. 1U (One Rack Unit) is approximately 1.75" in height, 2U is 3.5" in height, and so on. So for example, if you have 20 x 2U high servers you need to mount, you will need a server rack that has at least 40U of rack space - keeping in mind any room you need for a KVM switch, UPS, patch panel, etc.
42U Racks: 42U Server Racks are the most common rack height sold for data centers. 42U = 42 Rack Units on your Mounting Rails = 73.5" of rack mount space available. Please note that actual internal and external height vary depending on rack manufacturer.
Other Rack Heights: Depending on your application, requirements, and space limitations, a smaller more specialized rack may be best for your needs. Though it may be intuitive to think that a smaller rack would be less expensive because of less steel being used, racks in the 42U height range are mass produced and therefore usually have far less production cost. Following are links to other rack heights available.
After you select the depth that suits your needs, you can then select the height, manufacturer, and then configure your server rack to meet your specific requirements.
Actual Rack Depth: The measurements shown above are the server racks actual external depth measuring from the front of the rack to the rear.
Usable Rack Depth: Though most rack mounting rails are fully adjustable, all server racks have to allow a small amount of room (7/8" of an inch) on the front and rear for the rails to be mounted and doors to open. Therefore when calculating the depth you require please keep in mind that the usable depth will be 1 3/4" less then the actual depth. For example a 30" deep server rack will have 28 1/4" inches of usable "rail-to-rail" space.
30" Actual Depth = 28.25" Usable Depth
32" Actual Depth = 30.25" Usable Depth
36" Actual Depth = 34.25" Usable Depth
40" Actual Depth = 38.25" Usable Depth
While 40 & 42 inches are the most common depths for server racks, other depths are available. To find the right rack for you, start by selecting an appropriate depth below.
Comparing server racks can be a daunting task. Even comparing racks with similar dimensions can be like comparing apples to oranges. In addition to your dimensions requirements, please also take into consideration the rack's cooling capabilities and cooling options, compatibility, load capacity, cable management options, rack accessories, rail mounting, and overall rack expandability. For additional help, please contact our expert sales engineers at 1-866-722-5776.