NAME¶

pmdabtrfs - btrfs filesystem performance metrics domain agent (PMDA)

SYNOPSIS¶

$PCP_PMDAS_DIR/btrfs/pmdabtrfs [-D debug] [-d domain] [-l logfile]

DESCRIPTION¶

pmdabtrfs is a Performance Metrics Domain Agent (PMDA) which extracts performance metrics from the btrfs filesystem via sysfs (/sys/fs/btrfs).

The btrfs PMDA exports metrics covering filesystem information (label, sizes, generation, checksum algorithm), transaction commit statistics, space allocation for data, metadata and system block groups, per-device error statistics, and async discard statistics.

Metrics are organized into two instance domains: one for btrfs filesystems (keyed by UUID) and one for devices (keyed by UUID::devid). Labels are provided for each instance, including the filesystem UUID, label, and device ID where applicable.

A brief description of the pmdabtrfs command line options follows:

-d

The performance metrics domain number must be set to a unique value.

-l

Location of the log file. By default, a log file named btrfs.log is written in the current directory of pmcd(1) when pmdabtrfs 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.

INSTALLATION¶

The btrfs PMDA requires a Linux system with one or more mounted btrfs filesystems. The PMDA reads statistics from sysfs and does not require root privileges.

Install the PMDA using the Install script:

# cd $PCP_PMDAS_DIR/btrfs
# ./Install

To remove the PMDA use the Remove script:

# cd $PCP_PMDAS_DIR/btrfs
# ./Remove

DEBUGGING OPTIONS¶

The -D or --debug option enables the output of additional diagnostics on stderr to help triage problems, although the information is sometimes cryptic and primarily intended to provide guidance for developers rather end-users. debug is a comma separated list of debugging options; use pmdbg(1) with the -l option to obtain a list of the available debugging options and their meaning.

Debugging options specific to pmdabtrfs are as follows:

ENVIRONMENT¶

The BTRFS_PATH environment variable can be set to override the default sysfs path (/sys/fs/btrfs) for testing purposes.

SEE ALSO¶

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