VCS agents poll the resources periodically based on the monitor interval (in seconds) value that is defined in the MonitorInterval or in the OfflineMonitorInterval resource type attributes. After each monitor interval, VCS invokes the monitor agent function for that resource. For example, for process offline monitoring, the process agent's monitor agent function corresponding to each process resource scans the process table in each monitor interval to check whether the process has come online. For process online monitoring, the monitor agent function queries the operating system for the status of the process id that it is monitoring. In case of the mount agent, the monitor agent function corresponding to each mount resource checks if the block device is mounted on the mount point or not. In order to determine this, the monitor function does operations such as mount table scans or runs statfs equivalents.
With intelligent monitoring framework (IMF), VCS supports intelligent resource monitoring in addition to poll-based monitoring. IMF is an extension to the VCS agent framework. You can enable or disable the intelligent monitoring functionality of the VCS agents that are IMF-aware. For a list of IMF-aware agents, see the Cluster Server Bundled Agents Reference Guide.
Poll-based monitoring can consume a fairly large percentage of system resources such as CPU and memory on systems with a huge number of resources. This not only affects the performance of running applications, but also places a limit on how many resources an agent can monitor efficiently.
However, with IMF-based monitoring you can either eliminate poll-based monitoring completely or reduce its frequency. For example, for process offline and online monitoring, you can completely avoid the need for poll-based monitoring with IMF-based monitoring enabled for processes. Similarly for vxfs mounts, you can eliminate the poll-based monitoring with IMF monitoring enabled. Such reduction in monitor footprint will make more system resources available for other applications to consume.
With IMF-enabled agents, VCS will be able to effectively monitor larger number of resources.
Thus, intelligent monitoring has the following benefits over poll-based monitoring:
Provides faster notification of resource state changes
Reduces VCS system utilization due to reduced monitor function footprint
Enables VCS to effectively monitor a large number of resources
Consider enabling IMF for an agent in the following cases:
You have a large number of process resources or mount resources under VCS control.
You have any of the agents that are IMF-aware.
For information about IMF-aware agents, see the following documentation:
See the Cluster Server Bundled Agents Reference Guide for details on whether your bundled agent is IMF-aware.
See the Storage Foundation Cluster File System High Availability Installation Guide for IMF-aware agents in CFS environments.