NEC N8405-019, User Manual

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
There are three power redundancy modes; N+N redundant, N+1 redundant and
non-redundant.
–
In the N+N redundant mode, each power supply unit is divided into two groups to
configure the redundant power supply system. If a power supply in a group is defected,
only the power of the other group can maintain the system operation.
–
In the N+1 redundant mode, power supply units are not grouped but each power supply
unit is controlled individually. Using a power supply in addition to the number of
power supply units required for the normal system operation enables redundant power
system.
–
In the non-redundant mode, power supply units are turned on (DC output) for several
minutes, as is necessary for normal system operation. The power supply performance is
more efficient than the above redundant modes, and saves power. This mode is mainly
specified for using built-in UPS units. If this mode is specified for configurations
without built-in UPS units, the system may shut down due to a power supply unit
failure or other cause.
 The power control policy includes three modes; "CPU performance", "maintain
redundancy" and "recover redundancy".
–
The "CPU performance" mode makes the EM card prioritize the operation performance
of CPU blades. In this mode, if the EM card cannot accept a new power request from a
CPU blade with the power redundancy maintained, the EM card releases the power
redundant configuration and permits the new power request from the CPU blade. Note,
however, this mode is not supported in [4+0] status in the power supply system
configured with four power supply units. (If a power supply unit is defected during
operation under the release of the power redundant configuration, then the system may
be forcibly shut down.)
In the [N+N redundant mode], the electric power is not secured across the two power
supply systems. With the power system in which two power supply units are installed
in each system, the power shortage will occur if a new power request from the CPU
blade exceeds the capability of two power supply units. The EM card does not secure
the power equivalent to three power supply units across the two systems.
–
The "maintain redundancy" mode makes the EM card accept a new power request from
a CPU blade within the range allowing the power redundancy to be maintained. If the
EM card cannot accept a new power request from a CPU blade with the power
redundancy maintained, the EM card denies the request. In the "maintain redundancy"
mode, any measures are not taken if the power redundancy is lost due to an event such
as a failure of a power supply unit. (When a power supply unit is defected further in no
power redundancy status, the system may be shut down forcibly.)
–
The "recover redundancy" mode makes the EM card accept a new power request from
a CPU blade within the range allowing the power redundancy to be maintained and
limit the operation performance of CPU blades to suppress the power consumption for
recovery of the power redundancy if the redundancy is lost due to an event such as a
failure of a power supply unit. (Depending on operations of CPU blades, the EM card
cannot reduce the power consumption to the value allowing the power redundancy to
be recovered.)