Unbridled Cynicism

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RRD cheatsheet

This summarises a bunch of stuff from the RRD tutorial.

Data collection and storage in RRD

  • DS = Data Source
    • Has a name, type (counter, gauge, etc), heartbeat until considered unknown, mix, max
  • RRA = Round Robin Archive, an averaged timeline in the RRD; usually we keep 3-4 different RRAs for a given data source, with decreasing granularity and increasing retention
  • CF = Consolidation Function (for a given step)
    • Can be AVERAGE, MIN, MAX, LAST
    • xff = number of primary unknowns allowed per step before making the step Unknown
    • steps = how many Primary DPs to form a Consolidated DP
    • rows = number of generations of data to keep in an RRA

An example for sampling and consolidation: commonly you keep 24hrs of 5min samples, with 5min granularity. So that’s a 5min step, 1 primary DP per consolidated DP, kept for 288 gens 5min * 288 gens = 1440min per day).

Another RRA for a whole week would use the same DS, which means the same 5min sampling. 30min granularity would be 6 PDPs to make 1 CDP, probably using the AVERAGE consolidation function. Keep it for 336 generations (30min * 336 gens = 10080min per week).

Here’s a more realistic example in the tutorial.

Data extraction and graphing

  • DEF = Definition, extracts an RRA from an RRD file, eg. DEF myspeed = foo.rrd:speed:AVERAGE
  • CDEF = Calculated DEF, apply a transform to a DEF, eg. CDEF myspeedKMH = myspeed,3.6,*

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