


RRDTOOL(1)                   rrdtool                   RRDTOOL(1)


NAME
       rrdtool - round robin database tool

SYNOPSIS
       rrdtool - | function

DESCRIPTION
       OVERVIEW

       It is pretty easy to gather status information from all
       sorts of things, ranging from the temperature in your
       office to the number of octets which have passed through
       the FDDI interface of your router. But it is not so
       trivial to store this data in a efficient and systematic
       manner. This is where rrdtool kicks in. It lets you log
       and analyze the data you gather from all kinds of data-
       sources (DS). The data analysis part of rrdtool is based
       on the ability to quickly generate graphical
       representations of the data values collected over a
       definable time period.

       In this man page you will find general information on the
       design and functionality of the Round Robin Database Tool
       (rrdtool). For a more detailed description of how to use
       the individual functions of the rrdtool check the
       corresponding man page.

       For an introduction to the usage of rrdtool make sure you
       check the rrdtutorial manpage.

       FUNCTIONS

       While the man pages talk of command line switches you have
       to set in order to make rrdtool work it is important to
       note that the rrdtool can be 'remote controlled' through a
       set of pipes. This saves a considerable amount of startup
       time when you plan to make rrdtool do a lot of things
       quickly. Check the section on the section on "Remote
       Control" further down. There is also a number of language
       bindings for rrdtool which allow you to use it directly
       from perl, python, tcl, php, ...

       create  Set up a new Round Robin Database (RRD). Check the
               rrdcreate manpage.

       update  Store new data values into an RRD. Check the
               rrdupdate manpage.

       graph   Create a graph from data stored in one or several
               RRD. Apart from generating graphs, data can also
               be extracted to stdout. Check the rrdgraph
               manpage.





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RRDTOOL(1)                   rrdtool                   RRDTOOL(1)


       dump    Dump the contents of an RRD in plain ASCII. In
               connection with restore you can use it to
               transport an rrd from one architecture to another.
               Check the rrddump manpage.

       restore Restore an RRD in XML format to a binary rrd ...
               Check the rrdrestore manpage

       fetch   Get data for a certain time period from a RRD. The
               graph function uses fetch to retrieve its data
               from an rrd. Check the rrdfetch manpage.

       tune    Alter setup of an RRD. Check the rrdtune manpage.

       last    Find last update time of an RRD. Check the rrdlast
               manpage.

       rrdresize
               Change the size of individual RRAs ... Dangerous!
               Check the rrdresize manpage.

       xport   Export data retrieved from one or several RRD.
               Check the rrdxport manpage

       rrdcgi  This is a standalone tool for producing rrd graphs
               on the fly. Check the rrdcgi manpage.

       HOW DOES RRDTOOL WORK?


       Data acquisition
               When monitoring the state of a system, it is
               convenient to have the data available at a
               constant interval. Unfortunately you may not
               always be able to fetch data at exactly the time
               you want to. Therefore rrdtool lets you update the
               logfile at any time you want. It will
               automatically interpolate the value of the data-
               source (DS) at the latest official time-slot and
               write this value to the log. The value you have
               supplied is stored as well and is also taken into
               account when interpolating the next log entry.

       Consolidation
               You may log data at a 1 minute interval, but you
               are also be interested to know the development of
               the data over the last year. You could do this by
               simply storing the data in 1 minute interval, for
               one year. While this would take considerable disk
               space it would also take a lot of time to analyze
               the data when you wanted to create a graph
               covering the whole year. rrdtool offers a solution
               to this problem through its data consolidation
               feature. When setting up an Round Robin Database



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RRDTOOL(1)                   rrdtool                   RRDTOOL(1)


               (RRD), you can define at which interval this
               consolidation should occur, and what consolidation
               function (CF) (average, minimum, maximum, last)
               should be used to build the consolidated values
               (see rrdcreate). You can define any number of
               different consolidation setups within one RRD.
               They will all be maintained on the fly when new
               data is loaded into the RRD.

       Round Robin Archives
               Data values of the same consolidation setup are
               stored into Round Robin Archives (RRA). This is a
               very efficient manner to store data for a certain
               amount of time, while using a known amount of
               storage space.

               It works like this: If you want to store 1000
               values in 5 minute interval, rrdtool will allocate
               space for 1000 data values and a header area. In
               the header it will store a pointer telling which
               one of the values in the storage area was last
               written to. New values are written to the Round
               Robin Archive in a ...  you guess it ... round
               robin manner. This automatically limits the
               history to the last 1000 values. Because you can
               define several RRAs within a single RRD, you can
               setup another one, storing 750 data values at a 2
               hour interval and thus keeping a log for the last
               two months although at a lower resolution.

               The use of RRAs guarantees that the RRD does not
               grow over time and that old data is automatically
               eliminated. By using the consolidation feature,
               you can still keep data for a very long time,
               while gradually reducing the resolution of the
               data along the time axis. Using different
               consolidation functions (CF) allows you to store
               exactly the type of information that actually
               interests you. (Maximum one minute traffic on the
               LAN, minimum temperature of the wine cellar, total
               minutes down time ...)

       Unknown Data
               As mentioned earlier, the RRD stores data at a
               constant interval. Now it may happen that no new
               data is available when a value has to be written
               to the RRD. Data acquisition may not be possible
               for one reason or an other. The rrdtool handles
               these situations by storing an *UNKNOWN* value
               into the database. The value '*UNKNOWN*' is
               supported through all the functions of the
               database. When consolidating the amount of
               *UNKNOWN* data is accumulated and when a new
               consolidated value is ready to be written to its



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RRDTOOL(1)                   rrdtool                   RRDTOOL(1)


               Round Robin Archive (RRA) a validity check is
               performed to make sure that the percentage of
               unknown data in the new value is below a
               configurable level. If so, an *UNKNOWN* value will
               be written to the RRA.

       Graphing
               The rrdtool also allows one to generate reports in
               numerical and graphical form based on the data
               stored in one or several RRDs. The graphing
               feature is fully configurable. Size, color and
               contents of the graph can be defined freely. Check
               the rrdgraph manpage for more information on this.

       REMOTE CONTROL

       When you start rrdtool with the command line option '-',
       it waits for input via standard in. With this feature you
       can improve performance by attaching rrdtool to another
       process (mrtg is one example) through a set of pipes. Over
       the pipes rrdtool accepts the same arguments as on the
       command line. When a command is completed, rrdtool will
       print the string  '`OK'', followed by timing information
       of the form u:usertime s:systemtime both values are
       running totals of seconds since rrdtool was started. If an
       error occurs, a line of the form '`ERROR:' Description of
       error' will be printed. rrdtool will not abort if
       possible, but follow the ERROR line with an OK line.

SEE ALSO
       rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch,
       rrdtune, rrdlast, rrdxport

BUGS
       Bugs ? Features !

AUTHOR
       Tobias Oetiker <oetiker@ee.ethz.ch>



















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