PMDAJBD2(1)						      General Commands Manual						       PMDAJBD2(1)

NAME

       pmdajbd2 - journal block device (JBD) performance metrics domain agent (PMDA)

SYNOPSIS

       $PCP_PMDAS_DIR/jbd2/pmdajbd2 [-d domain] [-l logfile] [-j path] [-U username]

DESCRIPTION

       pmdajbd2  is  a Performance Metrics Domain Agent (PMDA) which extracts performance metrics from the Journal Block Device subsystem (version
       2) in the Linux kernel.	These metrics are exported by the kernel in procfs files, one file per block device.  The JBD2 subsystem  is  used
       by several filesystems including ext3, ext4 and ocfs2.

       The  jbd2 PMDA exports metrics that measure detailed journal transaction information, such as time spent waiting and locked, request rates,
       blocks used and so on.

       A brief description of the pmdajbd2 command line options follows (these are only relevant when running the PMDA as a daemon, and not  as  a
       shared library):

       -d   It	is  absolutely crucial that the performance metrics domain number specified here is unique and consistent.  That is, domain should
	    be different for every PMDA on the one host, and the same domain number should be used for the same PMDA on all hosts.

       -l   Location of the log file.  By default, when running as a daemon a log file named jbd2.log is written in the current directory of  when
	    pmdajbd2 is started, i.e.  $PCP_LOG_DIR/pmcd.  If the log file cannot be created or is not writable, output is written to the standard
	    error instead.  When running in shared library mode, and diagnostic information will  be  written  into  the  pmcd	log  file,  namely
	    $PCP_LOG_DIR/pmcd/pmcd.log.

       -j   Allows an alternate path to the jbd2 statistics files to be specified.  The default path is /proc/fs/jbd2.

       -U   User  account  under  which  to run the agent.  The default is the unprivileged "pcp" account in current versions of PCP, but in older
	    versions the superuser account ("root") was used by default.

INSTALLATION

       This PMDA is installed by default and in the shared library mode (rather than as a separate daemon to pmcd(1)).	Thus, the names, help text
       and values for the jbd2 performance metrics should always be available.

       If you do not use these metrics you can remove this PMDA, do the following as root:

	    # cd $PCP_PMDAS_DIR/jbd2
	    # ./Remove

       If you want to enable the installation again, do the following as root:

	    # cd $PCP_PMDAS_DIR/jbd2
	    # ./Install

       pmdajbd2  is  launched  by  pmcd(1) and should never be executed directly.  The Install and Remove scripts notify pmcd(1) when the agent is
       installed or removed.

FILES

       $PCP_PMCDCONF_PATH
		 command line options used to launch pmdajbd2
       $PCP_PMDAS_DIR/jbd2/help
		 default help text file for the jbd2 metrics
       $PCP_PMDAS_DIR/jbd2/Install
		 installation script for the pmdajbd2 agent
       $PCP_PMDAS_DIR/jbd2/Remove
		 undo installation script for the pmdajbd2 agent
       $PCP_LOG_DIR/pmcd/jbd2.log
		 default log file for error messages and other information from pmdajbd2

PCP ENVIRONMENT

       Environment variables with the prefix PCP_ are used to parameterize the file and directory names used by PCP.  On  each	installation,  the
       file  /etc/pcp.conf contains the local values for these variables.  The $PCP_CONF variable may be used to specify an alternative configura-
       tion file, as described in pcp.conf(5).

SEE ALSO

       PCPIntro(1), pmcd(1), pcp.conf(5) and pcp.env(5).

Performance Co-Pilot							PCP							       PMDAJBD2(1)