Difference between revisions of "19" rack sizes"

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Some devices have depth adapter brackets, half their depth, so that a device can be attached at its center (of mass, this means a little less force on the front panel).
 
Some devices have depth adapter brackets, half their depth, so that a device can be attached at its center (of mass, this means a little less force on the front panel).
  
This works fine for relatively light and/or shallow devices, such as many in audio and telephony.  Works for some computer hardware too, such as patch bays, short-depth switches, etc., but you wouldn't want it for full blown computers.
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This works fine for relatively light and/or shallow devices, such as many in audio and telephony.  Works for some computer hardware too, such as patch bays, short-depth switches, etc., but you wouldn't want it for full blown computers, particularly fewer-U.
  
  
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===Device height===
 
===Device height===
  
The height is measured in ([https://en.wikipedia.org/wiki/Rack_unit rack units], 1.75" / 44.50 mm).
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The height is measured in [https://en.wikipedia.org/wiki/Rack_unit rack units], where 1U is 1.75" / 4.45 cm.
  
 
Most things are 1U through 4U, but you can go higher:
 
Most things are 1U through 4U, but you can go higher:
 
* 1U and 2U devices include various switches and simpler servers
 
* 1U and 2U devices include various switches and simpler servers
* 4U servers are frequently consumer-tower-like cases that are ''also'' rack-mountable
 
 
* 3U are often servers
 
* 3U are often servers
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* 4U servers may be consumer-tower-like cases that are ''also'' rack-mountable
 
* larger devices (6U, even 8U and 10U) include things like many-disk bays, blade enclosures, large UPSes
 
* larger devices (6U, even 8U and 10U) include things like many-disk bays, blade enclosures, large UPSes
  
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'''Mount depth'''
 
'''Mount depth'''
  
In four-post (square-hole) racks, you typically mount on outside {{comment(relevant when the posts themselves have depth, rather than are strips with holes)}}.  
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In four-post (square-hole) racks, you typically mount on outside {{comment|(relevant when the posts themselves have depth, rather than are strips with holes)}}.  
 
The distance between front and back posts is not standard,
 
The distance between front and back posts is not standard,
 
and has increased over the years, starting at 19" and now usually at least 600mm (23.6").
 
and has increased over the years, starting at 19" and now usually at least 600mm (23.6").
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Your typical airy 42U racks are on the large and spacious side, to avoid any problems.
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Your typical large airy 42U datacenter racks are on the large and spacious side, to avoid any problems.
  
  

Latest revision as of 18:23, 10 November 2019

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)


Two or four posts

Two-post racks fixing devices only by their front panel

Some devices have depth adapter brackets, half their depth, so that a device can be attached at its center (of mass, this means a little less force on the front panel).

This works fine for relatively light and/or shallow devices, such as many in audio and telephony. Works for some computer hardware too, such as patch bays, short-depth switches, etc., but you wouldn't want it for full blown computers, particularly fewer-U.


Four-post racks are a better idea for heavier devices, which includes most servers.

Since four-post racks are often enclosed, and often for computers, it's common to be able to slide them out for easier maintenance.

There is no hard standard for depth, so slides tend to be adjustible in length.

There is no standardization to how slides attach to servers, so slides are vendor/series/device-specific.

Device width

The 19.0" (483mm) width includes the mounting ears, their hole-center to hole-center is 465mm (18.3")

To fit between the posts, a device must be at most 451mm (17.8")

Device height

The height is measured in rack units, where 1U is 1.75" / 4.45 cm.

Most things are 1U through 4U, but you can go higher:

  • 1U and 2U devices include various switches and simpler servers
  • 3U are often servers
  • 4U servers may be consumer-tower-like cases that are also rack-mountable
  • larger devices (6U, even 8U and 10U) include things like many-disk bays, blade enclosures, large UPSes


When computers stands its PCIe-style cards upright (e.g. relevant now that GPUs are popular):

  • 2U is the minimum for half-height cards
  • 3U us the minimum for full-height cards - but not a given, 4U is more comfortable.


Device/mount depth

This article/section is a stub — probably a pile of half-sorted notes, is not well-checked so may have incorrect bits. (Feel free to ignore, fix, or tell me)

Mount depth

In four-post (square-hole) racks, you typically mount on outside (relevant when the posts themselves have depth, rather than are strips with holes). The distance between front and back posts is not standard, and has increased over the years, starting at 19" and now usually at least 600mm (23.6").

Currently typical is around 29" / ~740mm, mostly because modern server depths are around there. Exact This varies per manufacturer, for example Dell is 28 7/8″, HP is 29 1/8″, IBM is 28 1/2″


Sliding rails are frequently designed to be depth-adjustable to fit various racks.


Some racks allow moving the posts / mount rails depth-wise.



Device depth

There is no strong standard for

  • the depth of the equipment
  • the inner depth available for devices
  • the outer depth (or width) of the rack itself


Historically many devices kept under 23" or 24" in depth (so under 610mm),

In modern servers you see things like

  • around 712mm / 28"
  • around 740mm / 29"
  • around 812mm / 32"


Your typical large airy 42U datacenter racks are on the large and spacious side, to avoid any problems.


Convention makes many racks 800mm or ~1000mm deep (inner depth?(verify)), which historically meant plenty of space for cabling, and also allowed devices to be a little deeper without problem.



See also