Dell PowerVault 775N (Rackmount NAS Appliance) - Manual (Page 24)

Marking the Rack
You must allow 2 U (88 mm or 3.5 inches) of vertical space for each system you install in the
two-post rack.
Universal-Hole Spacing Racks
Industry-standard two-post racks with universal-hole spacing have an alternating pattern of
three holes per U with center-to-center hole spacing (beginning at the top hole of a 1-U
space) of 15.9 mm, 15.9 mm, and 12.7 mm (0.625 inch, 0.625 inch, and 0.5 inch) for the
front and back vertical column of holes (see Figure 1-13).
Figure 1-13. Two-Post, Open-Frame Relay Rack Universal-Hole Spacing
i
44 mm 1.75 inches (1 U)
1
c
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c
c
c
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i k
15.9 mm (0.625 inch)
12.7 mm (0.5 inch)
15.9 mm (0.625 inch)
15.9 mm (0.625 inch)
1
Wide-Hole Spacing Racks
Some two-post racks with wide-hole spacing have an alternating pattern of two holes per U
with center-to-center hole spacing (beginning at the top hole of a 1-U space) of 31.7 mm
and 12.7 mm (1.25 inches and 0.5 inch) for the front and back vertical column of holes (see
Figure 1-14).
1-20 I R a c k I n s t a l l a t i o n G u i d e