IBM SAN192C-6, Installation, Service And User Manual

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A and sums the output power of operational PSUs. It does the same for the right
two columns (Grid B) and uses the minimum of the two as the available power
pool. To utilize maximum power the sum of power supply outputs of Grid A and
Grid B PSU bays must be equal.
For example, a system with four 3 kW PSUs in Grid A bays and three 3 kW PSUs
in Grid B bays and in grid redundancy mode has 12 kW available from Grid A and
9 kW from Grid B. The minimum of the two grids is 9 kW so 9 kW is allocated to
the available power pool and 9 kW are reserved. If either grid fails enough power
is reserved that the remaining power supplies can still meet the 9 kW commitment.
The output of the fourth PSU in Grid A is not considered in the calculations even
though it provides power.
Full redundancy mode
This mode supports both grid redundancy or N+1 redundancy. 50% of the power
supply output is allocated to the reserve pool and the other 50% of the power
supply outputs are allocated to the available power pool. The reserved power may
be used to backup either single power supply failures or a grid failure.
For example, a system with six 3 kW power supplies in grid redundancy mode has
a total of 18 kW. 9 kW are allocated to the available power pool and 9 kW are
allocated to the reserve pool. If a grid failure occurs (half of the power supplies
loose power) the full reserve power pool is available to meet the 9 kW
commitment. Otherwise, as single power supplies fail power is allocated to the
available pool from the remaining reserve power pool until the reserve power pool
is exhausted.
Note:
Once a single power supply has failed in this mode, grid redundancy is no
longer available.
Figure 19 shows how to connect power supplies in a SAN768C-6 for grid
redundancy
Figure 20 on page 40 shows how to connect power supplies in a SAN384C-6 for
grid redundancy
Figure 19. SAN768C-6 Grid-PSU Connections
Chapter 1. Introducing the IBM c-type SAN Directors
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