Chapter 6. Metrics Data Retention

The storage capacity required by PCP data logging is determined by the following factors:

  • the metrics being logged,
  • the logging interval,
  • and the retention policy.

The default logging (sampling) interval is 60 seconds.

The default retention policy is to keep archives for the last 14 days, compressing archives older than one day. PCP archive logs are stored in the /var/log/pcp/pmlogger/hostname directory.

6.1. Changing Default Logging Interval

This procedure describes how to change the default logging interval.

Procedure

  1. Edit the /etc/pcp/pmlogger/control.d/local configuration file.
  2. Edit the LOCALHOSTNAME line and append -t XXs, where XX is the desired time interval, measured in seconds.
  3. Restart the pmlogger service.

6.2. Changing Data Retention Policy

This procedure describes how to change the data retention policy.

Procedure

  1. Edit the /etc/cron.d/pcp-pmlogger file.
  2. Find the line containing pmlogger_daily.
  3. Change the value for parameter -x to the desired number of days after which data is archived.

  4. Add parameter -k, and add a value for the number of days after which data is deleted.

    For example, the parameters -x 4 -k 7 specify that data will be compressed after 4 days, and deleted after 7 days.

6.3. Confirming Data Storage Usage

To confirm data storage usage, enter the following command: 

# less /var/log/pcp/pmlogger/$(hostname)/pmlogger.log

This lists all available metrics, grouped by the frequency at which they are logged. For each group it also lists the storage required to store the listed metrics, per day.

Example storage statistics

logged every 60 sec: 61752 bytes or 84.80 Mbytes/day