Performance Co-Pilot PMDA for Monitoring GFS2 Filesystems
=========================================================

This PMDA is capable of collecting glock statistics from GFS2 filesystems
mounted on the system in both local and clustered configurations.

The PMDA collects its data from the trace-point output given by GFS2 as
the filesystem is working, this information is provided in userland
through debugfs. In order for pmdagfs2 to be able to provide any metric
data the user must have debugfs mounted and at least on GFS2 filesystem
mounted on the system to be monitored.

As mentioned above the PMDA can be used both situations where GFS2
filesystems are mounted as local filesystems and in cluster configurations
where GFS2 is used as a shared disk filesystem. When the PMDA is being
used in conjunction with a locally mounted filesystem (no clustering) only
a base number of metrics will be available to provide metric information
back to PMCD, these metrics can be recognised by their lack of
corresponding “control” metrics.

For configurations where GFS2 is used in a clustered environment the
additional “cluster only” metrics are able to collect data through the
cache control mechanism of the cluster. This data being passed between
cluster nodes regarding the state of glocks is unavailable in local
filesystem configurations leading the requirement for a cluster
configuration for these metrics.

For more information on GFS2 or cluster setups please visit www.redhat.com

Metrics
=======

The file ./help contains descriptions for all of the metrics which are
exposed by this PMDA.

Once the PMDA has been installed, the following command will list all of
the available metrics and their explanatory “help” text:

    + # $ pminfo -fT gfs2

Installation
============

    + # cd $PCP_PMDAS_DIR/gfs2

    + Check that there is no clash in the Performance Metrics Domain
      defined in ./domain.h and the other PMDA's currently in use (see
      $PCP_PMCDCONF_PATH). If there is, edit ./domain.h to choose another
      domain number (This should only be an issue on installations with
      third party PMDA's installed as the domain number given has been
      reserved for the GFS2 PMDA with base PCP installations).

    + Then simply use

        # ./Install

 	and choose both the “collector” and “monitor” installation
        configuration options.

Configuration
=============

Some of the metrics provided by the PMDA can be configured to whether they
are turned on or off with regards to collecting metric data. These metrics
are distinguished by having a corresponding “control” metric.

Identification of these metrics which have this control can be found by
issuing the following command.

    + $ pminfo -fT gfs2.control

The metrics given as output through pminfo in this way can be controlled
by setting their metric value to either 0 (Off: no collection of metric 
data) or 1 (On: collection of metric data) using the provided command
pmstore whilst specifying the metric to set the value for and a valid
value.

    + $ pmstore gfs2.control.tracepoints.all 1

Any metrics without a corresponding control metric cannot have their
functionality toggled in this way.

De-Installation
===============

    + Simply use

        # cd $PCP_PMDAS_DIR/gfs2
        #./Remove

Troubleshooting
===============

    + After installing or restarting the agent, the PMCD log file
      ($PCP_LOG_DIR/pmcd/pmcd.log) and the PMDA log file
      ($PCP_LOG_DIR/PMCD/gfs2.log) should be checked for any warnings or
      errors.

    + In an event where no values are being returned for most of the 
      metrics check ensure that both debugfs is mounted, metrics with 
      control options are enabled and your distribution supports the 
      full range of GFS2 trace-points.

          $ mount -t debugfs none /sys/kernel/debug

          $ pminfo -f gfs2.control

          $ pmstore gfs2.control.tracepoints.all 1
