EAR 4.3
Reference Manual
EAR Global Manager

Energy management

EARGM is a cluster wide component offering cluster energy monitoring and capping. EARGM can work in two modes: manual and automatic. When running in manual mode, EARGM monitors the total energy consumption, evaluates the percentage of energy consumption over the energy limit set by the admin and reports the cluster status to the DB. When running in automatic mode, apart from evaluating the energy consumption percentage it sends the evaluation to computing nodes. EARDs passes these messages to EARL which re-applies the energy policy with the new settings.

Apart from sending messages and reporting the energy consumption to the DB, EARGM offers additional features to notify the energy consumption: automatic execution of commands is supported and mails can also automatically be sent. Both the command to be executed or the mail address can be defined in the ear.conf, where it can also be specified the energy limits, the monitoring period, etc.

EARGM uses periodic aggregated power metrics to efficiently compute the cluster energy consumption. Aggregated metrics are computed by EARDBD based on power metrics reported by EARD, the per-node daemon.

Note: if you have multiple EARGMs running, only 1 should be used for Energy management. To turn off energy management for a certain EARGM simply set its energy value to 0.

Power capping

EARGM also includes an optional power capping system. Power capping can work in two different ways:

  • Cluster power cap (unlimited): Each EARGM controls the power consumption of the nodes under them by ensuring the global power does not exceed a set value. While the global power is under a percentage of the global value, the nodes run without any cap. If it approaches said value, a message is sent to all nodes to set their powercap to a pre-set value (via max_powercap in the tags section of ear.conf). Should the power go back to a value under the cap, a message is sent again so the nodes run at their default value (unlimited power).
  • Fine grained power cap control: Each EARGM controls the power consumption of the nodes under them and redistributes a certain budget between the nodes, allocating more to nodes who need it. It guarantees that any node has its default powercap allocation (defined by the powercap field in the tags section of ear.conf) if it is running an application.

Furthermore, when using fine grained power cap control it is possible to have multiple EARGMs, each controlling a part of the cluster, with (or without) meta-EARGMs redistributing the power allocation of each EARGM depending on the current needs of each part of the cluster. If no meta-EARGMs are specified, the power value each EARGM has will be static.

Meta-EARGMs are NOT compatible with the unlimited cluster powercap mode.

Configuration

The EAR Global Manager uses the $(EAR_ETC)/ear/ear.conf file to be configured. It can be dynamically configured by reloading the service.

Please visit the EAR configuration file page for more information about the options of EARGM and other components.

Additonally, 2 EARGMs can be used in the same host by declaring the environment variable EARGMID to specify which EARGM configuration each should use. If said variable is not declared, all EARGMs in the same host will read the first entry.

Execution

To execute this component, these systemctl command examples are provided:

  • sudo systemctl start eargmd to start the EARGM service.
  • sudo systemctl stop eargmd to stop the EARGM service.
  • sudo systemctl reload eargmd to force reloading the configuration of the EARGM service.