Compaq ProLiant BL e-Class System Overview and Planning

Compaq ProLiant BL e-Class System Overview and Planning 25
Determining Type and Number of PDUs: Redundant PDU Configuration
Use the following guidelines if using a redundant PDU configuration to survive a PDU failure or
PDU power cord unplug event. In this configuration, each power supply is connected to a
different PDU to eliminate the PDU as a single source of failure for that enclosure.
The input current rating for a fully-configured ProLiant BL e-Class server blade enclosure is 5 A
(200 to 240 VAC) or 10 A (100 to 120 VAC). This is the total current drawn by both enclosure
power supplies. To determine the number of server blade enclosures supported by a PDU, the
more restrictive of the following rules must be observed.
To ensure power supply 1 + 1 redundancy (only):
The total number of Amps drawn from the PDU should not exceed the input rating of the PDU.
The number of Amps drawn from any branch of the PDU should not exceed that branch’s output
breaker limit.
To ensure PDU redundancy:
If an enclosure has a power supply failure, the entire load (100%) for that enclosure shifts to the
PDU supporting the remaining supply. This additional 50% load must not exceed that branch
output breaker limit of the affected PDU.
Similar to the previous restriction, if a power supply fails, the re-distributed 50% load must not
exceed the input rating of the affected PDU.
To ensure AC source redundancy:
Each AC source (example, wall outlet) has a specified current rating and associated circuit
breaker specified by the facility’s owner. If an enclosure power supply failure or PDU failure
occurs, the total current requirement for the re-distributed load must not exceed the facility’s
rating for either redundant AC source.
Each AC source must be able to support 100% of the load of all equipment requiring AC source
redundancy. In the event of a total AC source failure, the total current requirement for all
enclosures, PDUs, and supporting equipment and monitors re-directs to the remaining AC source
and must not exceed the facility’s rating for that AC source.
IMPORTANT: Violation of any restriction could result in a “domino effect” that may disrupt
power to the enclosure, multiple enclosures, or the entire rack.