create - Set up a new Round Robin Database

# NAME

rrdtool create - Set up a new Round Robin Database

# SYNOPSIS

rrdtool create filename [--start|-b start time] [--step|-s step] [DS: ds-name: DST: heartbeat: min: max] [RRA: CF: xff: steps: rows]

# DESCRIPTION

The create function of the RRDtool lets you set up new Round Robin Database (RRD) files. The file is created at its final, full size and filled with *UNKNOWN* data.

filename
  The name of the RRD you want to create. RRD files should end with the extension .rrd. However, rrdtool will accept any filename.

--start|-b start time (default: now - 10s)
  Specifies the time in seconds since 1970-01-01 UTC when the first value should be added to the RRD. rrdtool will not accept any data timed before or at the time specified.

  See also AT-STYLE TIME SPECIFICATION section in the rrdfetch documentation for more ways to specify time.

--step|-s step (default: 300 seconds)
  Specifies the base interval in seconds with which data will be fed into the RRD.

DS:ds-name:DST:heartbeat:min:max
  A single RRD can accept input from several data sources (DS). (e.g. Incoming and Outgoing traffic on a specific communication line). With the DS configuration option you must define some basic properties of each data source you want to use to feed the RRD.

  ds-name is the name you will use to reference this particular data source from an RRD. A ds-name must be 1 to 19 characters long in the characters [a-zA-Z0-9_].

  DST defines the Data Source Type. It can be one of the following: GAUGE this is for things like temperatures or number of people in a room. COUNTER is for continuous incrementing counters like the InOctets counter in a router. The COUNTER data source assumes that the counter never decreases, except when a counter overflows. The update function takes the overflow into account. The counter is stored as a per-second rate. DERIVE will store the the derivative of the line going from the last to the current value of the data source. This can be useful for gauges, for example, to measure the rate of people entering or leaving a room. ABSOLUTE is for counters which get reset upon reading.

  heartbeat defines the maximum number of seconds that may pass between two updates of this data source before the value of the data source is assumed to be *UNKNOWN*.

  min and max are optional entries defining the expected range of the data supplied by this data source. If min and/or max are defined, any value outside the defined range will be regarded as *UNKNOWN*. If you do not know or care about min and max, set them to U for unknown. Note that min and max always refer to the processed values of the DS. For a traffic-COUNTER type DS this would be the max and min data-rate expected from the device.

  If information on minimal/maximal expected values is available, always set the min and/or max properties. This will help RRDtool in doing a simple sanity check on the data supplied when running update.

RRA:CF:xff:steps:rows
  The purpose of an RRD is to store data in the round robin archives (RRA). An archive consists of a number of data values from all the defined data-sources (DS) and is defined with an RRA line.

  When data is entered into an RRD, it is first fit into time slots of the length defined with the -s option becoming a primary data point.

  The data is also consolidated with the consolidation function (CF) of the archive. The following consolidation functions are defined: AVERAGE, MIN, MAX, LAST.

  xff The xfiles factor defines what part of a consolidation interval may be made up from *UNKNOWN* data while the consolidated value is sill regarded as known.

  steps defines how many of these primary data points are used to build a consolidated data point which then goes into the archive.

  rows defines how many generations of data values are kept in an RRA.

# EXAMPLE

`rrdtool create temperature.rrd --step 300 DS:temp:GAUGE:600:-273:5000 RRA:AVERAGE:0.5:1:1200 RRA:MIN:0.5:12:2400 RRA:MAX:0.5:12:2400 RRA:AVERAGE:0.5:12:2400`

This sets up an RRD called temperature.rrd which accepts one temperature value every 300 seconds. If no new data is supplied for more than 600 seconds, the temperature becomes *UNKNOWN*. The minimum acceptable value is -273 and the maximum is 5000.

A few archives areas are also defined. The first stores the temperatures supplied for 100 hours (1200 * 300 seconds = 100 hours). The second RRA stores the minimum temperature recorded over every hour (12 * 300 seconds = 1 hour), for 100 days (2400 hours). The third and the fourth RRA's do the same with the for the maximum and average temperature, respectively.

# AUTHOR

Tobias Oetiker <oetiker@ee.ethz.ch>