


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 triv-
       ial to store this data in a efficient and systematic man-
       ner. 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 corre-
       sponding man page.

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

       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 "Remote Control" further
       down. There is also a number of language bindings for RRD-
       Tool which allow you to use it directly from Perl, Python,
       Tcl, Php, ...

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

       update  Store new data values into an RRD. Check rrdup-
               date.

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

       dump    Dump the contents of an RRD in plain ASCII. In
               connection with restore you can use it to trans-
               port an RRD from one architecture to another.



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RRDTOOL(1)                   RRDtool                   RRDTOOL(1)


               Check rrddump.

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

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

       tune    Alter setup of an RRD. Check rrdtune.

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

       info    Display information about an RRD ... Check rrdinfo

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

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

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

       HOW DOES RRDTOOL WORK?


       Data acquisition
               When monitoring the state of a system, it is con-
               venient 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 interpo-
               late the value of the data-source (DS) at the lat-
               est 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 cover-
               ing the whole year. RRDTool offers a solution to
               this problem through its data consolidation fea-
               ture. When setting up an Round Robin Database
               (RRD), you can define at which interval this con-
               solidation should occur, and what consolidation



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RRDTOOL(1)                   RRDtool                   RRDTOOL(1)


               function (CF) (average, minimum, maximum, last)
               should be used to build the consolidated values
               (see rrdcreate). You can define any number of dif-
               ferent 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 val-
               ues 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 his-
               tory 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 consoli-
               dation functions (CF) allows you to store exactly
               the type of information that actually interests
               you. (Maximum one minute traffic on the LAN, mini-
               mum 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 sup-
               ported 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 Round Robin Archive
               (RRA) a validity check is performed to make sure
               that the percentage of unknown data in the new



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RRDTOOL(1)                   RRDtool                   RRDTOOL(1)


               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 fea-
               ture is fully configurable. Size, color and con-
               tents of the graph can be defined freely. Check
               rrdgraph 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 run-
       ning 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 possi-
       ble, but follow the ERROR line with an OK line.

SEE ALSO
       rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch, rrd-
       tune, rrdlast, rrdxport

BUGS
       Bugs ? Features !

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






















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