IBM SAN Volume Controller 2145-CF8, Hardware Installation Manual

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Redundant ac-power switch
The redundant ac-power switch is an optional feature that makes the SAN Volume
Controller nodes resilient to the failure of a single power circuit. The redundant
ac-power switch is not a replacement for an uninterruptible power supply. You
must still use a uninterruptible power supply for each node.
You must connect the redundant ac-power switch to two independent power
circuits. One power circuit connects to the main power input port and the other
power circuit connects to the backup power-input port. If the main power to the
SAN Volume Controller node fails for any reason, the redundant ac-power switch
automatically uses the backup power source. When power is restored, the
redundant ac-power switch automatically changes back to using the main power
source.
Place the redundant ac-power switch in the same rack as the SAN Volume
Controller node. The redundant ac-power switch logically sits between the rack
power distribution unit and the 2145 UPS-1U.
You can use a single redundant ac-power switch to power one or two SAN Volume
Controller nodes. If you use the redundant ac-power switch to power two nodes,
the nodes must be in different I/O groups. In the event that the redundant
ac-power switch fails or requires maintenance, both nodes turn off. Because the
nodes are in two different I/O groups, the hosts do not lose access to the back-end
disk data.
For maximum resilience to failure, use one redundant ac-power switch to power
each SAN Volume Controller node.
Figure 1 shows a redundant ac-power switch.
Cabling of redundant ac-power switch (example)
You must properly cable the redundant ac-power switch units in your
environment.
Note: While this topic provides an example of the cable connections, it does not
indicate a preferred physical location for the components.
Figure 2 on page 3 shows an example of the main wiring for a SAN Volume
Controller cluster with the redundant ac-power switch feature. The four-node
cluster consists of two I/O groups:
svc00297
Figure 1. Photo of the redundant ac-power switch
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IBM System Storage SAN Volume Controller: Model 2145-CF8 Hardware Installation Guide