What are EMS HA Monitors?

EMS HA Monitors (Event Monitoring Service High Availability Monitors) are a set of monitors and a monitoring service that polls a local system or application resource and sends messages when events occur. An event can simply be defined as something you want to know about. For example, you may want to be alerted when a disk fails or when available filesystem space falls below a certain level. EMS allows you to configure what you consider an event for any monitored system resource.

The advantage EMS has over built-in monitors is that requests can be made to send events to a wide variety of software using multiple protocols (opcmsg, SNMP, TCP, UDP). For example, you can configure EMS so that when a disk fails a message is sent to MC/ServiceGuard and IT/Operations. These applications can then use that message to trigger package failover and to send a message to an administrator to fix the disk.

EMS HA Monitors consist of a framework, a collection of monitors, and a configuration interface that runs under SAM (System Administration Manager). The framework starts and stops the monitors, stores information used by the monitors, and directs monitors where to send events. A standard API provides a way to add new monitors as they become available, or to write your own monitors; see the document Writing Monitors for the Event Monitoring Service (EMS) available from the high availability web site: http://www.hp.com/go/ha

Figure 1-1 Event Monitoring Services High Availability Monitors

Monitors are applications written to gather and report information about specific resources on the system. They use system information stored in places like /etc/lvmtab and the MIB database. When you make a request to a monitor, it polls the system information and sends a message to the framework, which then interprets the data to determine if an event has occurred and sends messages in the appropriate format.

EMS HA Monitors work best in a high availability environment; it aids in quickly detecting and eliminating single points of failure, and monitors resources that can be used as MC/ServiceGuard package dependencies. However, EMS HA Monitors can also be used outside a high availability environment for monitoring the status of system resources.

A set of monitors is shipped with EMS: disk, cluster, network interface, and system resource monitors. Other Hewlett-Packard products are bundled with monitors that fit into the EMS framework, such as ATM and HP OSI Transport Service 9000. You can also write your own monitor; see Writing Monitors for the Event Monitoring Service (EMS).