Users Guide

Redundancy policies
Redundancy policy is a configurable set of properties that determine how CMC manages power to the
chassis. The following redundancy policies are configurable:
• Grid Redundancy
• No Redundancy
• Redundancy Alerting Only
Grid Redundancy policy
The Grid Redundancy policy is also knows as 1+1 policy, for one active and one spare PSU.
The purpose of the Grid Redundancy policy is to enable an enclosure system to operate in a mode in
which the enclosure can tolerate AC power failures. These failures may originate in the AC power grid,
the cabling and delivery, or a Power Supply Unit (PSU) itself. When you configure a system for Grid
Redundancy, connect PSUs 1 and 2 to separate power grids.
In this mode, the CMC ensures that power usage is maintained such that the system continues to operate
with no degradation if there is a failure of either the grid or a single PSU. Server power-on is limited to the
available power of a single PSU. If at any time redundancy cannot be maintained (such as if a PSU is
removed or fails) alerts are triggered, the chassis health becomes
Critical.
No Redundancy policy
The No Redundancy policy is also known as 2+0 policy.
In this mode, all the power of both PSUs is available and used, but there is no assurance that a PSU or grid
failure does not affect system operation.
Redundancy Alerting Only policy (Default setting)
The Redundancy Alerting Only policy permits server power-on to use the capacity of both PSUs, while
alerting on actual conditions such as removal or failure of a PSU, or actual power consumption exceeding
the capabilities of a single PSU. This is the default policy.
PSU failures
PSU failures of any type are always alerted, regardless of the selected redundancy policy.
Default Redundancy configuration
Redundancy Alerting Only is the default redundancy configuration for a chassis and two PSUs.
Multi-node sled adaptation
The PowerEdge FM120x4 is a multi-node, half-width sled that can accommodate four servers with the
associated iDRAC with independent processors. It is designed for optimal power efficiency and the
processors cannot be removed. The processors in PowerEdge FM120 share a common power
infrastructure, for example, a single power and temperature sensors for the entire sled.
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