# RRD_STORAGE_TYPE = MULTIPLE

available starting with PNP 0.6.3

Since PNP version 0.6 it is possible to store performance data into multiple RRD databases instead of a single RRD database.

After creation of an RRD file you cannot alter the number of data sources. This may lead to problems if Nagios plugins change the number of data sources dynamically.

An example might be `check_disk` if you monitor all available file systems using one service. If a file system is added the RRD database cannot be updated anymore because the internal would be changed.

Per default PNP uses the option `RRD_STORAGE_TYPE = SINGLE` which is defined in `process_perfdata.pl` and might be changed using the config file `process_perfdata.cfg`. This setting should not be changed globally because PNP will start creating new RRD files immediately after changing to MULTIPLE. Old data will get lost!

Additionally it is not advisable to activate `RRD_STORAGE_TYPE = MULTIPLE` globally in regard to performance. The number of RRD databases and the disk I/O will increase significantly. That means that you should carefully select which Nagios check commands should be altered.

The section Custom Templates contains information about how the settings should be altered.

## A converter

The script `libexec/rrd_convert.pl` will be used to switch `RRD_STORAGE_TYPE` to `MULTIPLE` and to migrate the RRD databases.

Significant as always with PNP is the Nagios check command.

    rrd_convert.pl --check_command=<nagios_check_command> | --list_commands [ --dry-run ] [ --tmp_dir=<temp-directory ]
    [ --no_structure_check ]

You have to specify at least one of ”–check_command” or ”–list_commands”, respectively. Using the open `–check-command=` you tell the script which check command should be searched for.

`rrd_convert.pl` will now browse all PNP XML files for this command and output some statistics.

After confirmation from the user the conversion of the appropriate RRD databases will start displaying the progress. Pressing <ENTER> as an answer will terminate the script so please enter a letter.

If you are unsure then use `–list_commands` to get a list of the check commands used in the XML files.

The option `–dry-run` will convert the RRD databases but they will be stored in /tmp/rrd_convert in separate folders per host instead. This way you'll get a feeling about the runtime and the amount of data.

If you want to change the temporary directory you can use `–tmp_dir=<alternative temp dir>`.

Sometimes the number of datasources in the RRD files doesn't match the number in the XML files. This might happen if a plugin suddenly returns more datasources than usual (like check_disk as mentioned above). Using the option `–no_structure_check` these RRD files will be converted as well.

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