◦Thetotal "Maximum Draw" required to power allthe components configured within that
chassis—suchas I/O modules, fans, blade servers (CPU and memory configuration of the blade
servers).
◦TheDesired Power Redundancy for the chassis. The supported power configurations are
non-redundant,N+1 redundancy (or any requirement greater than N+1), and grid redundancy.
Toconfigure redundancy, see the Configuration Guide for the version of Cisco UCS Central that you are
using.The configurationguides are availableat the followingURL: http://www.cisco.com/en/US/products/
ps12502/products_installation_and_configuration_guides_list.html.
Non-redundant Mode
Ina non-redundant or combined mode, all installed power supplies are turned on and balance the load evenly.
Smallerconfigurations (requiring less than 2500 W) can be powered by a single power supply when the system
isusing Cisco UCS Release 1.3(1) or earlier releases. However, a single power supply cannot provide
redundancyand if either the power input or power supplyfail, the system immediately shuts down. More
commonconfigurations require two or more power supplies (if requirements are between 2500 and 5000 W
peak)in non-redundantmode.
Whenusing Cisco UCS Release 1.4(1) and later releases, the chassis requires a minimum of 2 power supplies.
Ina non-redundant system, power supplies can be inany slot. Installing less than the required number of
powersupplies resultsin undesired behaviorsuch as serverblade shutdown. Installingmore than the
requiredamount of power supplies may result in lower power supply efficiency.At most, this mode will
requiretwo power supplies.
Note
N+1 Redundancy
TheN+1 redundancy configuration implies that the chassis contains a total number of power supplies to satisfy
non-redundancy,plus one additional power supply for redundancy. All the power suppliesthat are participating
inN+1 redundancy are turned on andequally share the power load for thechassis. If any additional power
suppliesare installed, Cisco UCS Manager recognizes these “unnecessary”power supplies and places them
onstandby.
Ifa powersupply shouldfail, the surviving supplies can provide power to the chassis. In addition, UCS
Managerturns on any "turned-off"power supplies to bring the system back to N+1 status.
Toprovide N+1 protection, the following number of power supplies is recommended:
•Threepower supplies are recommended if the power configuration for that chassis requires greater than
2500W or if using UCS Release 1.4(1) and later releases
•Twopower supplies are sufficient if the power configuration for that chassis requires less than 2500 W
orthe system is using UCS Release 1.3(1) or earlier releases
Addingan additional power supply to either of these configurations will provide an extra level of protection.
CiscoUCS Manager turns on the extra power supply in theevent of a failureand restores N+1 protection.
Cisco UCS 5108 Server Chassis Installation Guide
22 OL-20035-05
Overview
Power Supplies