APCUPSD

The APCUPSD dameon allows the helios cluster to communicate with the APC power supply units. It is used to trigger an emergency shutdown when a long term loss of power has been detected. By initiating a shut down when power runs low, we hope to prevent the loss of data and damage to the hardware. The large number of nodes makes it impossible to find a single power supply that would serve all of the computers in the event of a power loss, consequently we have four identical power supplies that each serve for machines. We however do not monitor the status of each power supply and instead we assume that they are all at the same state, because of this only one of the power supplies is connected to the headnode by a USB connection. Using the APCUPSD software we have configured the headnode to execute a script when it detects that power remaining in the batteries is 5% or less. At this time the script in '/etc/apcupsd/doshutdown' is executed. This script in turns executes the PHP script ;/root/management/clustershutdown' that shutsdown the cluster. We decided on this approach rather than using the built in network capacities of APCUPSD to keep a single shutdown mechanism.

Information on the documentation of APCUPSD is available here: http://www.apcupsd.org/manual/index.html