I. Introduction:
1- What is a 19″ server rack?
A 19″ server rack generally refers to equipment installed in a 19″ cabinet or rack. The difference between a cabinet and a rack is that a cabinet has a protective cover and top and bottom covers, while a rack does not.
Racks, as distinct from cabinets, are often called “frames.” Both are rectangular in shape. The 19″ server chassis was designed to fit inside a cabinet, assuming a rectangular shape and complying with specific height limitations so that chassis produced by different manufacturers can fit into cabinets designed with the same specifications.
2- Origins of 19″ server racks and cabinets
Originally, 19″ server racks and cabinets were a standard for US military electronic control instruments. The objective of this standard was to unify the dimensions of these devices and facilitate their rapid assembly, replacement and maintenance. Eventually, this standard was adopted by the civil sector, becoming widely used in the business world.
3- Types of 19″ server rack products
3-1- The advantages of cabinets include providing protection for server racks and facilitating expansion. They were initially used for industrial control systems, but in recent years, due to the development of networks, they have been increasingly used for network communication equipment.
Therefore, its product types can be broadly divided into two main categories: products for office use and products for industrial use.
3-2- Products for office use
- 3-2-1- Servers
- 3-2-2- Telecommunications products
- 3-2-3- Internet/Intranet products
- 3-2-4- Other products related to computer peripherals
3-3- Products for industrial use
- 3-3-1- IPC (Industrial PC)
- 3-3-2- Control panels
- 3-3-3- Other related machine-assisted products
II. 19″ Server Rack Outside Dimensions and Cabinet Specifications
1- Cabinet Specifications
Cabinets are not just boxes as the name suggests; they come in various formats, as shown in the three figures below. All of these cases are HP products, but their appearance and dimensions vary depending on the operating environment.
All enclosures are manufactured to relevant specifications, with defined widths, heights and depths covered in the IEC-60297 and EIA-310 series. Both specifications define the height unit as U (1U = 1.75″ = 44.45mm), the width as 19″ (there are other width specifications, but 19″ is the most common), and the depth has some variation.
1-1- Definition of U height unit: 1U = 1.75 inches = 44.45mm. Cabinets use U as the basic unit, so a 35U cabinet can accommodate a total height of 35U of server racks, but the total height of the cabinet is not 35U.
1-2- The width definition of 19 inches (482.6 mm) refers to the maximum visible width of the server rack when viewed from the front, which is generally the width of the mounting flanges on each side of the server rack, not the width of the cabinet itself. The width of 19″ cabinets is limited by the dimensions of the server racks, almost always exceeding 500mm (as 19″ server racks are around 483mm wide). Current case widths on the market range from 500mm to 800mm, with some special specifications exceeding 1000mm, but the most common is a 600mm wide case.
1-3- Although there are regulations for cabinet depth, they are rarely mentioned as they do not limit server rack designs such as height and width. Even short server racks can be used in long cabinets as long as their design specifications are fully compatible. Cabinet manufacturers produce various depth specifications, with 600mm, 700mm and 800mm deep cabinets being the most commonly used (depth refers to the outer depth of the cabinet, excluding handles).
2- Relationship between the external appearance of the server rack and the cabinet during design
2-1- External dimensions: The design of the server rack is limited by the size of the cabinet, therefore, designers must consider the following points:
2-1-1- In terms of height: As height is measured in U, with 1U equal to 1.75″ or 44.45mm, a 1U server rack cannot exceed 44.45mm in height. To facilitate stacking and assembly, the height is typically designed to be less than 44 mm. Likewise, the actual height of server racks with different U-values will be slightly less than the U-value, allowing space between each server rack in the cabinet for easier assembly and disassembly.
2-1-2- In terms of width: 19″ cabinets have sheet metal (or rectangular aluminum) columns at each corner to support the cabinet and secure the server rack, so the internal width available for the server racks server is only about 450 mm (approximately 17.7″), not the full width of 19″. To account for mounting, the width of the server rack cannot be set to 450mm and generally does not exceed 440mm, leaving a gap of 5mm on each side. If slide rails are considered to facilitate assembly, maintenance and disassembly, the width of the server rack must be further reduced. Common thicknesses of slide rails range from 10 to 20 mm, and both sides need rails, so the width of the server rack becomes even narrower after accounting for double the thickness.
2-1-3- In terms of depth: Depth considerations include the need for server racks within cabinets to have space for heat dissipation, cable management, and other component arrangements. Since space on both sides is limited, designers must utilize the front and rear spaces. There is typically at least 75mm of space at the front and back (depending on the location of the mounting bracket). Therefore, for a 600mm cabinet, it is better to design server racks with a depth of less than 450mm.
2-2- Cabinet Mounting Holes: Server racks must be secured on both sides when placed in a cabinet, with mounting holes usually located on the mounting flanges. The dimensions and positions of these holes are shown in the figure below (data source: EIA-310-D). The figure shows three width dimensions, each with three numbers. The top tier of dimensions is the standard size for 19-inch cabinets (i.e., 450, 465, and 483.4). The three dimensions represent the following:
450mm – Maximum width that a server rack can occupy inside the cabinet. 465mm – Distance between the mounting holes in the server rack and the cabinet. 483.4mm – Maximum width allowed between mounting flanges on the server rack.
31.8 mm – Distance between the two mounting holes at a height of 1U. If there are three mounting holes at a height of 1U, the distance between the holes will be half of 31.8 mm, that is, 15.9 mm.
12.7 mm – Closest distance between the mounting holes of two adjacent U units, specifically, the distance between the bottom hole of the top U and the top hole of the bottom U. The junction between 1U and 1U is located in the middle of the 12.7 mm distance.
6.75 mm – Distance between the top (or bottom) mounting hole of the server rack and the top (or bottom) inside of the cabinet.
2-3- Front Handles: Server racks are pushed in and out from the front, so handles are usually designed on the front sides of the server rack for ease of operation. When designing handles, care must be taken to avoid interfering with the screw mounting holes for mounting the server rack and cabinet, as these holes are also located on the sides of the server rack.
2-4- Foot pads: Some server racks are designed to operate independently outside the cabinet, so their bases are often equipped with feet. This prevents damage to surfaces when placed on a table or desk. However, when installing the server rack in a cabinet, the feet may interfere with the server rack below. As a result, it is preferable to design foot pads that can be easily removed and reinstalled.
III. Standard 19-inch Cabinet Size Chart
The standard case we commonly see is the standard 19-inch case. Nowadays, most engineering equipment panel widths use the 19-inch size specification. As a result, the 19-inch case became a natural standard case.
Regarding the standard case, we know that its structure is not very complicated, usually consisting of the basic case structure, internal support system and power and cooling system components.
The purpose of standardizing server dimensions is to ensure that the server maintains the proper size to be placed in a metal or aluminum rack. The rack has screw holes for fixing the server by aligning them with the screw holes on the server and then fixing it with screws to facilitate the space required for each server.
The standard dimensions of a server are width (48.26 cm = 19 inches) and height (a multiple of 4.445 cm). Because the width is 19 inches, sometimes a rack that meets this standard is also called a “19-inch rack.” Thickness is based on a unit of 4.445cm, with 1U equal to 4.445cm.
Specific dimensions and size standards are shown in the chart below:
Standard 19-inch cabinet dimensions
| Item | Type | Size/mm |
|---|---|---|
| Standard Cabinet | 18U | 1000X600X600 |
| 24U | 1200X600X600 | |
| 27U | 1400X600X600 | |
| 32U | 1600X600X600 | |
| 37U | 1800X600X600 | |
| 42U | 2000X600X600 | |
| Server Cabinet | 42U | 2000X800X800 |
| 37U | 1800X800X800 | |
| 24U | 1200X600X800 | |
| 27U | 1400X600X800 | |
| 32U | 1600X600X800 | |
| 37U | 1800X600X800 | |
| 42U | 2000X600X800 | |
| Wall mounted cabinet | 6U | 350X600X450 |
| 9U | 500X600X450 | |
| 12U | 650X600X450 | |
| 15U | 800X600X450 | |
| 18U | 1000X600X450 |
42U enclosure dimensions
The dimensions of the 42U case are quite similar to the standard 19-inch case, with the only difference being the height, which is 42U. The height of equipment installed in a standard 19-inch cabinet is expressed in a special unit called “U”, where 1U is equivalent to 44.45mm.
Equipment panels for devices that utilize standard 19-inch enclosures are generally made to the nU standard. For a 42U case, the available internal space is 42U, allowing you to choose the size of the case based on the number of devices you have.
Totem cases offer 18U, 22U, 27U, 32U, 37U, 42U and 47U options for you to choose from.
How are the dimensions of a cabinet defined? Let's take a look at a more detailed introduction below, hoping it helps with selecting a case.
The height dimensions H 1 series can be seen in the table below:
| H1 | 600 | 800 | 1000 | 1200 | 1400 | 1500 | 1800 | 2000 | 2200 | 2600 |
| H2 | 9U | 13U | 18U | 22U | 27U | 31U | 36U | 40U | 450 | 54U |
Note: In the table, 1U = 44.45mm. When there is no need for combined cabinets, H 1 is the reference dimension.
Server cabinet dimensions explained:
When we talk about the “U” of a server, it is a unit that represents the external dimensions of the server. It is an abbreviation for “Unit” and is determined by the American Electronics Industry Association (EIA) as an industry standard. The purpose of standardizing server dimensions is to ensure that servers maintain adequate dimensions to fit into iron or aluminum racks.
The standard dimensions of a server are width (48.26 cm = 19 inches) and height (multiples of 4.445 cm). Because the width is 19 inches, racks that meet this standard are also called “19-inch racks,” which is the width of a rack-mounted server.
Choosing Server Cabinet Space Considerations:
Plan and list all equipment to be installed in the cabinet and their precise measurements: height, length, width and weight. By summing up the volume and space occupied by these devices, you will ultimately decide the height of the case you will choose. Clearly, taller cabinets can accommodate more equipment and save space.
Maximizing cabinet height is not the only consideration; the rear of the case also has a large area available for use. This is the reason to measure the depth of the cabinet. Choosing a deeper enclosure allows you to install two sets of equipment back to back and then install even more devices.
After calculating the cabinet space (in “U” or 1.75-inch drives), consider the overall size of the cabinet. No one would like to discover that they need to add more equipment right after filling the cabinet. Therefore, as a general rule, allow an extra 20% to 30% in cabinet height for system expansion. This extra space also improves equipment ventilation.
