Notes on RRD file name nomenclature

Usually, RRD files are located in /var/lib/munin/[ group ]/[ node name ]-[ service name ]-[ field name ]-[ a/c/d/g ].rrd

Example:

/var/lib/munin/SomeGroup/foo.example.com-cpu-irq-d.rrd
               --------- --------------- --- --- -
                   |            |         |   |  `-- Data type (a = absolute, c = counter, d = derive, g = gauge)
                   |            |         |   `----- Field name / data source: 'irq'
                   |            |         `--------- Plugin name: 'cpu'
                   |            `------------------- Node name: 'foo.example.com'
                   `-------------------------------- Group name: 'SomeGroup'

When loaning data from other graphs, the {fieldname}.type must be set to the same data type as the original data. If not, Munin default to searching for gauge files, i.e. files ending with -g.rdd.

Example on loaning data:

01    [foo.example.com]
02        if_total.update no
03        if_total.graph_order \
04            load=bar.example.com:if_eth0.bps
05        if_total.load.label Network traffic
06        if_total.load.type COUNTER

If the {fieldname}.type is set to COUNTER, munin-graph will search for the file bar.example.com-if_eth0-bps-c.rdd.

If it is not set to COUNTER, Munin defaults the data type to GAUGE and searches for the file bar.example.com-if_eth0-bps-g.rdd - which does not exist. (Note the 'g' close to the end of the file name.)