IBM DS5100 Installation, User's, And Maintenance Manual page 157

Rack power cable connector
Rack power cable
ac distribution unit
power cord
Figure 89. Redundant ac power connections to controllers and storage expansion enclosures
For details about power requirements, see "Electrical requirements" on
page 29.
10. Go to "Turning on the storage subsystem" on page 131.
Attention:
Before you power on the DS5100 and DS5300, the storage subsystem must
be cabled to at least one storage expansion enclosure populated with the
minimum number of drives for the storage expansion enclosure. Otherwise, the
DS5100 and DS5300 controllers do not successfully complete the power-on
process and operate optimally.
All drives in the connected storage expansion enclosure or enclosures must
contain no prior configuration data. Additionally, if at least two drives are not
installed in each EXP5000 attached storage expansion enclosure, or at least
four drives in each EXP5060 storage expansion enclosure, the resulting
insufficient load to the storage expansion enclosure power supplies might
cause the drive expansion enclosure power supplies to intermittently appear as
failed and then reappear in an optimal state, falsely indicating that the power
supplies are bad.
Storage expansion
enclosure
power supplies
Controller power supplies
ac distribution units
Chapter 3. Cabling the storage subsystem
125