User's Manual

Grid Redundancy
In Grid redundancy mode with four PSUs, all four PSUs are active. The two PSUs must connect to one AC
power grid, while the other two PSUs are connect to the other AC power grid.
CAUTION: To avoid a system failure, and for Grid redundancy to work effectively, there must be a
balanced set of PSUs properly cabled to separate AC grids.
If one AC grid fails, the PSUs on the functioning AC grid take over, without interrupting the servers or
infrastructure.
CAUTION: In Grid redundancy mode, you must have balanced sets of PSUs (at least one PSU in
each grid). If this condition is not met, Grid redundancy is not possible.
Power Supply Redundancy
When power supply redundancy is enabled, a PSU in the chassis is kept as a spare, ensuring that the
failure of any one PSU does not cause the servers or chassis to turn off. Power supply redundancy mode
requires minimum two PSUs. Additional PSUs, if present, are utilized to improve power efficiency of the
system if DPSE is enabled. Subsequent failures after loss of redundancy may cause the servers in the
chassis to turn off.
Power Budgeting For Hardware Modules
CMC offers a power budgeting service that allows you to configure power budget, redundancy, and
dynamic power for the chassis.
The power management service enables optimization of power consumption and reallocation of power
to different modules on the basis of demand.
CMC maintains a power budget for the enclosure that reserves the necessary wattage for all installed
servers and components.
CMC allocates power to the CMC infrastructure and the servers in the chassis. CMC infrastructure
consists of components in the chassis, such as fans, I/O module, and storage adapters, PCIe cards,
physical disk, main board. The chassis may have up to four servers that communicate to the chassis
through an iDRAC. For more information, see the iDRAC7 User’s Guide at dell.com/support/manuals.
iDRAC provides CMC with its power envelope requirements before powering up the server. The power
envelope consists of the maximum and minimum power requirements necessary to keep the server
operating. iDRAC’s initial estimate is based on its initial understanding of components in the server. After
operation commences and further components are discovered, iDRAC may increase or decrease its initial
power requirements.
When a server is turned on in an enclosure, the iDRAC software reestimates the power requirements and
requests a subsequent change in the power envelope.
CMC supplies the requested power to the server, and the allocated wattage is subtracted from the
available budget. After the server is granted a power request, the server's iDRAC software continuously
monitors the actual power consumption. On the basis of actual power requirements, the iDRAC power
envelope may change over a period of time. iDRAC requests a power step up if the servers are fully using
the allocated power.
Under heavy load, the performance of the processors on the server may be degraded to ensure power
consumption stays lower than the user-configured System Input Power Cap.
The PowerEdge VRTX enclosure can supply enough power for peak performance of most server
configurations, but many available server configurations do not consume the maximum power that the
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