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 15 on page 25 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 71 for an example of redundant power cabling.
AC distribution unit
power cord
Controller power supplies
Storage expansion
enclosure
power supplies
Rack power cable connector
Rack power cable
AC distribution units
f10ug060
Figure 71. Redundant AC power connections to controllers and storage expansion enclosures
Chapter 3. Cabling the storage subsystem 99
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