user manual

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The total "Maximum Draw" required to power all the components configured within that
chassis—such as I/O modules, fans, blade servers (CPU and memory configuration of the blade
servers).
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The Desired 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.
To configure redundancy, see the Configuration Guide for the version of Cisco UCS Central that you are
using. The configuration guides are available at the following URL: http://www.cisco.com/en/US/products/
ps12502/products_installation_and_configuration_guides_list.html.
Non-redundant Mode
In a non-redundant or combined mode, all installed power supplies are turned on and balance the load evenly.
Smaller configurations (requiring less than 2500 W) can be powered by a single power supply when the system
is using Cisco UCS Release 1.3(1) or earlier releases. However, a single power supply cannot provide
redundancy and if either the power input or power supply fail, the system immediately shuts down. More
common configurations require two or more power supplies (if requirements are between 2500 and 5000 W
peak) in non-redundant mode.
When using Cisco UCS Release 1.4(1) and later releases, the chassis requires a minimum of 2 power supplies.
In a non-redundant system, power supplies can be in any slot. Installing less than the required number of
power supplies results in undesired behavior such as server blade shutdown. Installing more than the
required amount of power supplies may result in lower power supply efficiency. At most, this mode will
require two power supplies.
Note
N+1 Redundancy
The N+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 supplies that are participating
in N+1 redundancy are turned on and equally share the power load for the chassis. If any additional power
supplies are installed, Cisco UCS Manager recognizes these “unnecessary” power supplies and places them
on standby.
If a power supply should fail, the surviving supplies can provide power to the chassis. In addition, UCS
Manager turns on any "turned-off" power supplies to bring the system back to N+1 status.
To provide N+1 protection, the following number of power supplies is recommended:
•
Three power supplies are recommended if the power configuration for that chassis requires greater than
2500 W or if using UCS Release 1.4(1) and later releases
•
Two power supplies are sufficient if the power configuration for that chassis requires less than 2500 W
or the system is using UCS Release 1.3(1) or earlier releases
Adding an additional power supply to either of these configurations will provide an extra level of protection.
Cisco UCS Manager turns on the extra power supply in the event of a failure and restores N+1 protection.
Cisco UCS 5108 Server Chassis Installation Guide
22 OL-20035-05
Overview
Power Supplies