EMS Hardware Monitors: Glossary

The following terms are important for understanding hardware event monitors.

asynchronous event detection

The ability to detect an event at the time it occurs. When an event occurs the monitor is immediately aware of it. This method provides quicker notification response than polling.

default monitoring requests

The default monitoring configuration created when the EMS Hardware Monitors are installed. The default requests ensure that a complete level of protection is automatically provided for all supported hardware resources.

Event Monitoring Service (EMS)

The application framework used for monitoring system resources on HP-UX 10.20 and 11.0. Hardware monitoring uses the EMS framework for reporting events and creating PSM monitoring requests. A collection of EMS system monitors are available at additional cost and are not included with the hardware monitoring software. For more information on the EMS monitor, refer to Using EMS HA Monitors, which can be downloaded from http://docs.hp.com/hpux/ha/

event severity level

Each event that occurs within the hardware is assigned a severity level, which reflects the impact the event may have on system operation. The severity levels provide the mechanism for directing event notification. For example, you may choose a notification method for critical events that will alert you immediately to their occurrence, and direct less important events to a log file for examination at your convenience. Also, when used with MC/ServiceGuard to determine failover criteria, severe and critical events cause failover.

hardware event

Any unusual or notable activity experienced by a hardware resource. For example, a disk drive that is not responding, or a tape drive that does not have a tape loaded. When any such activity occurs, the occurrence is reported as an event to the event monitor.

hardware event monitor

A monitor daemon that gathers information on the operational status of hardware resources. Each monitor is responsible for watching a specific group or type of hardware resources. For example, the tape monitor handles all tape devices on the system. The monitor may use polling or asynchronous event detection for tracking events. Unlike a status monitor, an event monitor does not "remember" the occurrence of an event. It simply detects and reports the event. An event can be converted into a more permanent status condition using the Peripheral Status Monitor.

hardware resource

A hardware device used in system operation. Resources supported by hardware monitoring include mass storage devices such as disks and tapes, connectivity devices such and hubs and multiplexors, and device adapters.

MC/ServiceGuard

Hewlett-Packard's application for creating and managing high availability clusters of HP 9000 Series 800 computers. A high availability computer system allows application services to continue in spite of a hardware or software failure. Hardware monitoring integrates with MC/ServiceGuard to ensure that hardware problems are detected and reported immediately, allowing MC/ServiceGuard to take the necessary action to maintain system availability. MC/ServiceGuard is available at additional cost.

monitoring request

A group of settings that define how events for a specific monitor are handled by EMS. A monitoring request identifies the severity levels of interest and the type of notification method to use when an event occurs. A monitoring request is applied to each hardware device (or instance) supported by the monitor. Monitoring requests are created for hardware events using the Hardware Monitoring Request Manager. Monitoring requests are created for changes in hardware status using the EMS GUI.

Peripheral Status Monitor (PSM)

Included with the hardware event monitors, the PSM is a monitor daemon that acts as a hardware status monitor by converting events to changes in hardware resource status. This provides compatibility with MC/ServiceGuard, which uses changes in status to manage cluster resources. The PSM is also used to create hardware status monitoring requests through the EMS GUI.

polling

The process of connecting to a hardware resource at regular intervals to determine its status. Any events that occur between polling intervals will not be detected until the next poll, unless the monitor supports asynchronous event monitoring.

resource instance

A specific hardware device. The resource instance is the last element of the resource path and is typically the hardware path to the resource (e.g., 10_12_5.0.0), but it may also be a product ID as in the case of AutoRAID disk arrays. There may be multiple instances for a monitor, each one representing a unique hardware device for which the monitor is responsible.

resource path

Hardware event monitors are organized into classes (and subclasses) for creating monitoring requests. These classes identify the unique path to each hardware resource supported by the monitor. Two similar resource paths exist for each hardware resource - an event path used for creating event monitoring requests, and a status path used for creating PSM monitoring requests.