• In a Power Supply Redundancy configuration, in addition to the PSUs required to power the enclosure, the enclosure alwayskeeps an additional PSU powered on and marked Online. Power utilization is monitored and one PSU can be moved to Standbystate on the basis of overall system load. In a four PSU configuration, a minimum of two PSUs are always turned on.Because an enclosure in the Power Supply Redundancy configuration always has an extra PSU engaged, the enclosure canaccommodate the loss of one online PSU and still have enough power for the installed server modules. The loss of the onlinePSU causes a standby PSU to come online. Simultaneous failure of multiple PSUs may result in the loss of power to some servermodules while the standby PSUs are turning on.• In Grid Redundancy configuration, all PSUs are engaged when the chassis is turned on. Power utilization is monitored, and ifsystem configuration and power utilization allows, PSUs are moved to the Standby state. Because the Online status of PSUs ina grid mirrors that of the other grid, the enclosure can sustain the loss of power to an entire grid with no interruption of power tothe enclosure.An increase in power demand in the Grid Redundancy configuration cause the engagement of PSUs from the Standby state.This maintains the mirrored configuration needed for dual-grid redundancy.NOTE: With DPSE in enabled state, if power demand increases in both the two Power Redundancy policy modes, thestandby PSUs are brought Online to reclaim power.Default Redundancy ConfigurationAs shown in the table here, the default redundancy configuration for a chassis depends on the number of PSUs that it contains.Table 36. Default Redundancy ConfigurationPSU Configuration Default Redundancy Policy Default Dynamic PSU Engagement SettingTwo PSUs DC Redundancy DisabledFour PSUs DC Redundancy DisabledGrid RedundancyIn Grid redundancy mode with four PSUs, all four PSUs are active. The two PSUs must connect to one AC power grid, while theother 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 PSUsproperly 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 thiscondition is not met, Grid redundancy is not possible.Power Supply RedundancyWhen power supply redundancy is enabled, a PSU in the chassis is kept as a spare, ensuring that the failure of any one PSU does notcause 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 causethe servers in the chassis to turn off.Power Budgeting For Hardware ModulesCMC 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 thebasis 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 thechassis, such as fans, I/O module, and storage adapters, PCIe cards, physical disk, main board. The chassis may have up to fourservers that communicate to the chassis through an iDRAC. For more information, see the iDRAC User’s Guide at dell.com/support/manuals.156
