This article needs additional citations for verification .(December 2017) |
A rack unit (abbreviated U or RU) is a unit of measure defined as 1+3⁄4 inches (44.45 mm). [1] [2] It is most frequently used as a measurement of the overall height of 19-inch and 23-inch rack frames, as well as the height of equipment that mounts in these frames, whereby the height of the frame or equipment is expressed as multiples of rack units. For example, a typical full-size rack cage is 42U high, while equipment is typically 1U, 2U, 3U, or 4U high.
The rack unit size is based on a standard rack specification as defined in EIA-310. The Eurocard specifies a standard rack unit as the unit of height; it also defines a similar unit, horizontal pitch (HP), used to measure the width of rack-mounted equipment. The standard was adopted worldwide as IEC 60297 Mechanical structures for electronic equipment – Dimensions of mechanical structures of the 482.6 mm (19 in) series, and defines the sizes for rack, subrack (a shelf-like chassis in which cards can be inserted), and the pitch of printed circuit boards/cards providing physical compatibility of technological equipment, typically in telecommunications.[ citation needed ]
While a rack unit is defined as 1+3⁄4 inches (44.45 mm), a front panel or filler panel in a rack is not an exact multiple of this height. To allow space between adjacent rack-mounted components, a panel is 1⁄32 inches (0.03125 in or 0.794 mm) less in height than the full number of rack units would imply. Thus, a 1U front panel would be 123⁄32 inches (1.71875 in or 43.66 mm) tall. If n is number of rack units, the ideal formula for panel height is h = (1.75n − 0.031) for calculating in inches, and h = (44.45n − 0.794) for calculating in millimetres. Manufacturing allows for dimensions with less precision.
The 19-inch rack format with rack units of 1.75 inches (44.45 mm) was established as a standard by AT&T around 1922 in order to reduce the space required for repeater and termination equipment in a telephone company central office. [3]
A typical full-size rack is 42U, [4] which means it holds just over 6 feet (180 cm) of equipment, and a typical "half-height" rack is 18–22U, which is around 3 feet (91 cm) high.
Rack unit | inches | mm |
---|---|---|
1U | 1.75 | 44.45 |
2U | 3.5 | 88.9 |
3U | 5.25 | 133.35 |
4U | 7 | 177.8 |
5U | 8.75 | 222.25 |
6U | 10.5 | 266.7 |
7U | 12.25 | 311.15 |
8U | 14 | 355.6 |
9U | 15.75 | 400.05 |
10U | 17.5 | 444.5 |
11U | 19.25 | 488.95 |
12U | 21 | 533.4 |
13U | 22.75 | 577.85 |
14U | 24.5 | 622.3 |
15U | 26.25 | 666.75 |
16U | 28 | 711.2 |
17U | 29.75 | 755.65 |
18U | 31.5 | 800.1 |
19U | 33.25 | 844.55 |
20U | 35 | 889 |
21U | 36.75 | 933.45 |
22U | 38.5 | 977.9 |
23U | 40.25 | 1022.35 |
24U | 42 | 1066.8 |
25U | 43.75 | 1111.25 |
26U | 45.5 | 1155.7 |
27U | 47.25 | 1200.15 |
28U | 49 | 1244.6 |
29U | 50.75 | 1289.05 |
30U | 52.5 | 1333.5 |
31U | 54.25 | 1377.95 |
32U | 56 | 1422.4 |
33U | 57.75 | 1466.85 |
34U | 59.5 | 1511.3 |
35U | 61.25 | 1555.75 |
36U | 63 | 1600.2 |
37U | 64.75 | 1644.65 |
38U | 66.5 | 1689.1 |
39U | 68.25 | 1733.55 |
40U | 70 | 1778 |
41U | 71.75 | 1822.45 |
42U | 73.5 | 1866.9 |
The mounting-hole distance (as shown to the right) differs for 19-inch racks and 23-inch racks: 19-inch racks use uneven spacings (as shown to the right) while 23-inch racks use evenly spaced mounting holes. Although it is called a 19-inch rack unit, the actual mounting dimensions of a 19-inch rack unit are 185⁄16 inches (18.3125 in or 465.1 mm) [5] wide, center to center.
Rack units are universally the same, but the type of thread [6] can vary depending on the rack. Mounting rails can be No. 10-32 tapped (Unified Thread Standard), No. 12-24 tapped, metric M6 threaded or universal square holes. Universal square holes are becoming the most common as these allow the insertion of replaceable cage nuts for the type of thread needed.[ citation needed ] This prevents stripping of the threading on the rails and allows for more flexibility.
Whereas there is no formal specification for "half rack", the term half-rack can have different separate meanings: It can describe equipment that fits in a certain number of rack units, but occupy only half the width of a 19-inch rack (9.5 inches (241.30 mm)). These are commonly used when a piece of equipment does not require full rack width, but may require more than 1U of height.[ citation needed ] For example, a "4U half-rack" DVCAM deck occupies 4U (7 in) height × 9.5 in width, and in theory, two 4U half-rack decks could be mounted side by side and occupy the 4U space. It can also describe a unit that is 1U high and half the depth of a 4-post rack (such as a network switch, router, KVM switch, or server), such that two units can be mounted in 1U of space (one mounted at the front of the rack and one at the rear). When used to describe the rack enclosure itself, the term "half-rack" typically means a rack enclosure that is half the height (22U tall). There is also a "half rack width" size being used in IT applications where a device conforms to a smaller than 9.5-inch width so that these "half rack width" appliances may be used in a chassis system that fits the traditional 19-inch rack space, but allows for these 8.4-inch-wide "half rack width" appliances to be inserted and removed easily without tools or the need to remove adjacent hardware. This "half rack width" concept is popular in applications where IT equipment is being used by military who are unable to use traditional 1U full-depth IT appliances due to their large size.
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls.
Eurocard is an IEEE standard format for printed circuit board (PCB) cards that can be plugged together into a standard chassis which, in turn, can be mounted in a 19-inch rack. The chassis consists of a series of slotted card guides on the top and bottom, into which the cards are slid so they stand on end, like books on a shelf. At the spine of each card is one or more connectors which plug into mating connectors on a backplane that closes the rear of the chassis.
A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is 19 inches (482.6 mm) wide. The 19 inch dimension includes the edges or ears that protrude from each side of the equipment, allowing the module to be fastened to the rack frame with screws or bolts. Common uses include computer servers, telecommunications equipment and networking hardware, audiovisual production gear, music production equipment, and scientific equipment.
A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and keep clear of platforms, trackside buildings and structures. Classification systems vary between different countries, and gauges may vary across a network, even if the track gauge is uniform.
The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.
A blade server is a stripped-down server computer with a modular design optimized to minimize the use of physical space and energy. Blade servers have many components removed to save space, minimize power consumption and other considerations, while still having all the functional components to be considered a computer. Unlike a rack-mount server, a blade server fits inside a blade enclosure, which can hold multiple blade servers, providing services such as power, cooling, networking, various interconnects and management. Together, blades and the blade enclosure form a blade system, which may itself be rack-mounted. Different blade providers have differing principles regarding what to include in the blade itself, and in the blade system as a whole.
A computer case, also known as a computer chassis, is the enclosure that contains most of the hardware of a personal computer. The components housed inside the case are referred as the internal hardware, while hardware outside the case are known as peripherals.
A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed.
A cage nut or caged nut consists of a nut in a spring steel cage which wraps around the nut. The cage has two wings that when compressed allow the cage to be inserted into the square holes, for example, in the mounting rails of equipment racks. When the wings are released, they hold the nut in position behind the hole. Cage nuts conforming to this description were patented in 1952 and 1953. The original design requires an insertion tool to install a cage nut into a hole. Newer designs featuring squeeze-and-release tabs allow for tool-less installation.
A screw thread is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread. A screw thread is the essential feature of the screw as a simple machine and also as a threaded fastener.
ISO 5775 is an international standard for labeling the size of bicycle tires and rims. The system used was originally developed by the European Tyre and Rim Technical Organisation (ETRTO). It is designed to make tire sizing consistent and clear. It replaces overlapping informal systems that ambiguously distinguished between sizes. For example, at least 6 different "26 inch" sizes exist, and "27 inch" wheels have a larger diameter than American "28 inch" wheels. The Japanese Industrial Standards Committee also cooperates with ISO 5775. The corresponding Japanese standards are JIS D 9112 for tires and JIS D 9421 for rims.
Kitchen cabinets are the built-in furniture installed in many kitchens for storage of food, cooking equipment, and often silverware and dishes for table service. Appliances such as refrigerators, dishwashers, and ovens are often integrated into kitchen cabinetry. There are many options for cabinets available at present.
A DIN rail is a metal rail of a standard type widely used for mounting circuit breakers and industrial control equipment inside equipment racks. These products are typically made from cold rolled carbon steel sheet with a zinc-plated or chromated bright surface finish. Although metallic, they are meant only for mechanical support and are not used as a busbar to conduct electric current, though they may provide a chassis grounding connection.
British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basis for many other standards, such as BSF, BSP, BSCon, and BSCopper.
A rack rail, or rack strip, is used to mount rackable electronic hardware and 19-inch rack mount accessories within a 19-inch rack. Within a rack a minimum of two rack rails are required to mount equipment. The height of rack rail is determined by the number of rack units required for mounting the equipment.
Strut channel, often referred to colloquially by one of several manufacturer trade names, is a standardized formed structural system used in the construction and electrical industries for light structural support, often for supporting wiring, plumbing, or mechanical components such as air conditioning or ventilation systems.
Horizontal pitch (HP) is a unit of length defined by the Eurocard printed circuit board standard used to measure the horizontal width of rack mounted electronic equipment, similar to the rack unit (U) used to measure vertical heights of rack mounted equipment. One HP is 0.2 inches (5.08 mm) wide. A standard 19-inch rack is 95 HP wide of which 84 HP is typically usable. A standard 23-inch rack is 115 HP wide of which 104HP is typically usable.
A KVM is a computer input/output device offering the combination of a keyboard, video monitor and mouse. They are typically constructed to fit into a 19-inch rack although there are manufacturers who offer a KVM that can be mounted to a flat surface such as a control console.
The NEC SX-Aurora TSUBASA is a vector processor of the NEC SX architecture family. Unlike previous SX supercomputers, the SX-Aurora TSUBASA is provided as a PCIe card, termed by NEC as a "Vector Engine" (VE). Eight VE cards can be inserted into a vector host (VH) which is typically a x86-64 server running the Linux operating system. The product has been announced in a press release on 25 October 2017 and NEC has started selling it in February 2018. The product succeeds the SX-ACE.
Racks are measured in rack units (RU or U) with the industry standard being 42U tall — about 6 feet.