IBM DS4800 - Page 112

4. On each RAID controller, remove the nut that holds the power cable
strain-relief clamp, and then remove the strain-relief clamp.
5. Wrap the strain-relief clamp around the line jumper power cord approximately
20 cm (8 in.) from the RAID controller connection end. Leave some slack
between the clamp and the RAID controller end of the line jumper power cord.
6. Replace the strain-relief clamp, and then tighten it securely with the nut.
7. Connect the other end of the line jumper cords to two independent
IBM-approved power distribution units in the rack cabinet. Connecting each
RAID controller to independent power sources maintains power redundancy. If
applicable, repeat this step for each additional storage subsystem and storage
expansion enclosure.
8. Connect the right and left power supplies of the attached storage expansion
enclosures to the same IBM-approved power distribution units in the rack
cabinet. For more information, refer to the Installation, User’s, and
Maintenance Guide for your DS4000 storage expansion enclosures.
9. If you have not already done so, connect the primary power cables from the
rack cabinet to the external power source.
Note: To maintain power redundancy, plug the PDUs that power the storage
subsystem’s right and left RAID controllers and the right and left power
supplies of the DS4000 storage expansion enclosures into two
independent external power circuits through ac distribution units inside a
rack cabinet or directly into external receptacles.
It is recommended that you determine the maximum surge current
possible when all devices in the power circuit are started at the same
time. Based on the total number of devices on a power circuit, find the
maximum (worst-case) specification value in order to prevent the circuit
from tripping. When both RAID controllers are connected and the
storage subsystem is powered on, each RAID controller unit will handle
approximately one-half of the current load. To ensure maximum
protection against power loss due to RAID controller unit failure or a
power circuit tripping, both RAID controller units must be connected and
powered on. See Table 13 on page 23 for the DS4800 AC power
requirements.
Do not overload the circuits that power your storage subsystem and
storage expansion enclosures. Use additional pairs of IBM-approved
power distribution units (PDUs) if necessary.
See Figure 68 on page 91 for an example of redundant power cabling.
90 IBM System Storage DS4800 Storage Subsystem: Installation, User’s, and Maintenance Guide