It’s important to have power redundancy in mission-critical network. Below are some of the device support or has a power redundancy feature.
Cisco Catalyst 4500 Series: Redundant Mode – Use one power supply fail, Second power supply immediately supports the switch without any disruption on the network. Both power supplies must be the same wattage. A single power supply must have enough power to support the switch configuration.
Combine Mode – Combined mode uses the power from all installed power supplies to support the switch configuration power requirements. However, combined mode has no power redundancy. If a power supply fails, one or more modules might shut down.
Commands: #show power – view power details (config)# no hw-module module num power – Turn power down to specified module (config)# hw-module module num power – Turn on the specified module. (config)# power redundancy-mode combined – Sets the power management mode to combine mode.
Cisco Catalyst 6500 Series: Redundant Mode – Both are running. Each power supply operates at ~50% of its capacity.
Combine Mode – Each power supply provides up to 83% of its capacity.
Q’s: How does switch determine which module’s power be turned off first?
It goes from the bottom module to the top module, with the exception of the Supervisor module, that’s turned off last. The above behavior is only seen during bootup, not while adding modules in a running switch.
If you have a running switch and try to insert a module which exceeds power requirement, the module won’t be turned on and current working modules won’t be turned off.
Cisco Nexus: Combined – This mode does not provide redundancy. The power available to the system is the sum of power outputs of all power supplies in the chassis. Power Supply Redundancy (N+1) – This mode guards against failure of one of the power supplies. The redundant power available to the system is the sum of all power outputs less one of the maximum rated power supplies.
** A single power supply must have enough power to support the switch configuration/Module.
Input Source Redundancy (Grid Redundancy) – This mode guards against failure of one power supply or input circuit (grid). The power available to the system is the minimum power from both grids. If one of the power supplies fails, the operational power redundancy mode changes to the combined mode (Only supported with 220V). Power supply and input source redundancy (full redundancy) – This mode guards against the failure of one power supply or one grid. The power available is the minimum power from the input source and power supply redundancy. If one of the power supplies fails, the operational power redundancy mode changes to the power supply redundancy (N+1) mode.
Cisco UCS: Non Redundant – Used all the power supply in the chassis for all of the server in the chassis. N+1 – The total number of power supplies to satisfy non-redundacy, plus one additional power supply for redundacy, are turned on and equally share the power load for the chassis. Grid – Two power sources are turned on, or the chassis requires greater than N+1 redundancy. If one source fails, the other power supply on the other power circuit continue to provide power to the chassis.