Fault Tolerance Features - IBM NeXtScale System Planning And Implementation Manual

Fan modules
Also shared in the chassis are 10 80 mm fan modules, five in each of the two
cooling zones.
The fan modules and PSUs in the chassis provide shared power and cooling
for all the installed nodes by using fewer components and with less power
than traditional systems.
For more information about the fan modules, see 3.5, "Fan modules" on
page 42.
Fan and Power Controller
The Fan and Power Controller (FPC) module is the management device for
the chassis and, as its name implies, controls the power and cooling features
of the enclosure.
For more information about the FPC, see 3.7, "Fan and Power Controller" on
page 47.
You might notice that the enclosure does not contain space for network switches.
All I/O is routed directly out of the servers to top-of-rack switches. This
configuration provides choice and flexibility and keeps the IBM NeXtScale n1200
Enclosure flexible and low cost.

3.1.3 Fault tolerance features

The chassis implements a fault tolerant design. The following components in the
chassis enable continued operation if one of the components fails:
Power supplies
The power supplies support a single power domain that provides DC power to
all of the chassis components. If a power supply fails, the other power
supplies can continue to provide power.
Power policies: The power management policy that you implemented for
the chassis determines the affect on chassis operation if there is a power
supply failure. Power policies can be N+N, N+1, or no redundancy. Power
policies are managed by the FPC.
Fan modules
The fan modules provide cooling to all of the chassis components. The power
supplies have their own fans to provide the cooling. Each fan module has a
dual rotor (blade) dual motor fan. One of the motors within the fan module can
fail and the remaining continue to operate. If a fan fails, the chassis continues
operating and the remaining fans increase in speed to compensate.
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IBM NeXtScale System Planning and Implementation Guide