Reference Guide

7.7
3PAR InServ E-Class/F-Class Storage Server Physical Planning Manual
7.3.2 RETMA Rail Spacing
The Radio Electronics Television Manufacturers Association (RETMA) railing is a standard of
rack spacing. An E200 and F200 node chassis requires 4U of spacing and an F400 requires 8U of
space. The drive chassis requires 3U of spacing. The actual physical height of a service processor
is 1U, but it requires 2U of spacing in the rack for servicing. See Figure 7-5 for the RETMA rack
spacing diagram.
■ One Rack Unit (RU or U) is 1.75 inch (44.45 mm) and contains three holes spaced by 1/4 inch.
■ The space between a rack unit is 1/8 inch.
Figure 7-5. Spacing Dimensions of RETMA Rails
1RU/1U
1.75 Inch
(44.45mm)
1/4
Inch
1/8
Inch
1/4
Inch
1/8
Inch
2
1
3
4
5
3
3
Square Hole Round Hole
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