rrdtool
RRDTOOL(1) rrdtool RRDTOOL(1)NAME
rrdtool - round robin database toolSYNOPSIS
rrdtool - | functionDESCRIPTION
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 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 Con trol" 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 man page. 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. 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. 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 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 of this problem through its data consolida tion feature. When setting up an Round Robin Database (RRD), you can define at which interval this consolidation should occur, and what consoli dation function (CF) (average, minimum, maximum, total, last) should be used to build the consoli dated 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 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 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 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 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 BUGS Bugs ? Features !AUTHOR
Tobias Oetiker <oetiker@ee.ethz.ch>