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Power distribution strategy
All power for the blades comes from a single 48 V intermediate power bus. Great
care is taken at each load to assure the integrity of the power bus.
The power supplies also provide a separate 12 V AUX voltage. This is used
throughout the system to power the I²C logic and to monitor and control different
system states.
ac input
Each ac input has an on-off circuit breaker switch. The power supply modules
include input power filtering and power indicator LEDs. The power supply output
remains within specific regulation for a minimum of 20 msec after the ac mains
have been disconnected.
Two detachable line cords provide ac input power to the chassis.
dc outputs
The 2109 Model M12 uses up to four power supplies. All power supplies are
hot-swappable. Two power supplies receive input power from one of the ac inputs.
The remaining two power supplies receive power from the other ac input. Only two
power supplies are required to run a completely loaded chassis. Therefore, if one
ac input fails, and all power supply modules are populated, the chassis continues to
run uninterrupted. If a power supply module fails, the remaining power supply
modules continue to provide uninterrupted power to the chassis. The power
supplies are plugged directly into their power bays to an internal blind connector.
Each blade assembly has separate dc-dc converter bricks for each voltage that is
required. This allows local regulation at the blade assembly, and provides for future
flexibility to match voltage needs with blade assembly type.
To maximize system availability when the switch blade assembly is plugged, it is
initially powered off by the hardware. This ensures that adding a blade assembly
does not bring the whole switch down if inadequate power is available. The system
confirms sufficient power for the new module and then applies power. If sufficient
power is not available (for example, if only one of the possible four power supplies
are installed), the system does not allow more than four switch blade assemblies
plus two CP blades to be powered up.
2N power architecture
The 2N power architecture is designed to protect against the loss of ac power. The
2109 Model M12 offers four power supply modules to assure maximum availability.
Under normal operating conditions, only two power supplies are needed for full
system operation. However, to ensure redundancy, two additional power supplies
are available and are added in pairs, one per ac source.
8
IBM TotalStorage SAN Switch: 2109 Model M12 User's Guide
Table 2. Power distribution system specifications (continued)
Specification
Under voltage protection
Value
The 2109 Model M12 power supply self-protects from any
input voltage, static or dynamic, from zero volts to its
operating ranges. It recovers to normal operation when it
returns to its operating range.
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