IBM s-series, Инструкция по установке и эксплуатации, Страница: 49 / 170

About redundant power supplies and power supply failure
A chassis with redundant power supplies can maintain full operation when one or
more power supplies fail. Power supply failure can be a failure of the supply itself or
the office power grid connected to the power supply.
A chassis can be either 1 + 1 redundant or N + 1 redundant. 1 + 1 redundancy
implies that for every power supply, there is another redundant (backup) power
supply. In other words, half of the supplies in the system can fail, and the system
will still operate normally.
N + 1 redundancy implies that there is one redundant
power supply for N power supplies, where N is a number greater than one. for
example, 3 + 1 redundancy means that in a system with four power supplies, the
system will continue to operate normally if one power supply fails, but will not
operate if more than one power supplies fail.
Power consumption is equally distributed (within a certain percentage depending on
power load or power supply type) among all power supplies in the system. When a
power supply fails, the power load is redistributed equally among the remaining
power supplies. Note that power consumption between POE and System power
supplies is not shared, meaning loss of a System power supply does not impact a
POE power supply, and vice versa.
What happens when one or more system power supplies fail
If one or more System power supplies fail and the system is left with less than the
minimum number of power supplies required for normal operation, the power
supplies will go into overload and the system will start to shut down. Several things
can happen. The output voltage of the remaining good power supplies will likely
drop as they try unsuccessfully to generate more power than they are capable of.
The system will react to a drop in voltage by increasing the current draw. The
hardware will shut down due to over-current protection or under-voltage protection,
whichever takes place first. One by one, the interface modules shut down until the
power is within the power budget of the remaining power supplies. There is no
particular order in which the interface modules will shut down, as this will occur in
hardware and not in software. The management CPU requires power as well, and
may also shut down during a power supply failure.
After a power loss, if the system is left with less than the minimum number of power
supplies required for normal operation, the system will be left in an unknown state.
At this point, manual recovery is required (restore power and power-cycle the
chassis).
What happens when one or more POE power supplies fail
If one or more POE power supplies fail and the system is left with less than the
minimum number of POE power supplies, the POE power supplies will go into
overload. Non-POE functions will not be impacted, provided the System power
supplies are still up and running. Several things can happen with a POE power
supply failure. The output voltage of the remaining good power supplies will likely
drop as they try unsuccessfully to generate more power than they are capable of.
The system will react to a drop in voltage by increasing the current draw. The
hardware will shut down POE function due to over-current protection or
under-voltage protection, whichever occurs first. The interface modules will start to
shut down its POE ports one by one until the over-power is within the power budget
of the remaining power supplies. There is no particular order in which the POE
ports will shut down, as this occurs in hardware and not in software.
Chapter 2. Product Overview
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