1RRDTOOL(1) rrdtool RRDTOOL(1)
2
6 rrdtool - Round Robin Database Tool
7
9 rrdtool - [workdir]| function
10
12 OVERVIEW
13 It is pretty easy to gather status information from all sorts of
14 things, ranging from the temperature in your office to the number of
15 octets which have passed through the FDDI interface of your router. But
16 it is not so trivial to store this data in an efficient and systematic
17 manner. This is where RRDtool comes in handy. It lets you log and
18 analyze the data you gather from all kinds of data-sources (DS). The
19 data analysis part of RRDtool is based on the ability to quickly
20 generate graphical representations of the data values collected over a
21 definable time period.
22 In this man page you will find general information on the design and
24 functionality of the Round Robin Database Tool (RRDtool). For a more
25 detailed description of how to use the individual functions of RRDtool
26 check the corresponding man page.
27 For an introduction to the usage of RRDtool make sure you consult the
29 rrdtutorial.
30 FUNCTIONS
32 While the man pages talk of command line switches you have to set in
33 order to make RRDtool work it is important to note that RRDtool can be
34 remotely controlled through a set of pipes. This saves a considerable
35 amount of startup time when you plan to make RRDtool do a lot of things
36 quickly. Check the section on Remote_Control further down. There is
37 also a number of language bindings for RRDtool which allow you to use
38 it directly from Perl, python, Tcl, PHP, etc.
39 create Set up a new Round Robin Database (RRD). Check rrdcreate.
41 update Store new data values into an RRD. Check rrdupdate.
43 updatev Operationally equivalent to update except for output. Check
45 rrdupdate.
46 graph Create a graph from data stored in one or several RRDs. Apart
48 from generating graphs, data can also be extracted to stdout.
49 Check rrdgraph.
50 graphv Create a graph from data stored in one or several RRDs. Same as
52 graph, but metadata are printed before the graph. Check
53 rrdgraph.
54 dump Dump the contents of an RRD in plain ASCII. In connection with
56 restore you can use this to move an RRD from one computer
57 architecture to another. Check rrddump.
58 restore Restore an RRD in XML format to a binary RRD. Check rrdrestore
60 fetch Get data for a certain time period from a RRD. The graph
62 function uses fetch to retrieve its data from an RRD. Check
63 rrdfetch.
64 tune Alter setup of an RRD. Check rrdtune.
66 first Find the first update time of an RRD. Check rrdfirst.
68 last Find the last update time of an RRD. Check rrdlast.
70 lastupdate
72 Find the last update time of an RRD. It also returns the value
73 stored for each datum in the most recent update. Check
74 rrdlastupdate.
75 info Get information about an RRD. Check rrdinfo.
77 resize Change the size of individual RRAs. This is dangerous! Check
79 rrdresize.
80 xport Export data retrieved from one or several RRDs. Check rrdxport.
82 flushcached
84 Flush the values for a specific RRD file from memory. Check
85 rrdflushcached.
86 HOW DOES RRDTOOL WORK?
88 Data Acquisition
89 When monitoring the state of a system, it is convenient to have
90 the data available at a constant time interval. Unfortunately,
91 you may not always be able to fetch data at exactly the time
92 you want to. Therefore RRDtool lets you update the log file at
93 any time you want. It will automatically interpolate the value
94 of the data-source (DS) at the latest official time-slot
95 (interval) and write this interpolated value to the log. The
96 original value you have supplied is stored as well and is also
97 taken into account when interpolating the next log entry.
98 Consolidation
100 You may log data at a 1 minute interval, but you might also be
101 interested to know the development of the data over the last
102 year. You could do this by simply storing the data in 1 minute
103 intervals for the whole year. While this would take
104 considerable disk space it would also take a lot of time to
105 analyze the data when you wanted to create a graph covering the
106 whole year. RRDtool offers a solution to this problem through
107 its data consolidation feature. When setting up an Round Robin
108 Database (RRD), you can define at which interval this
109 consolidation should occur, and what consolidation function
110 (CF) (average, minimum, maximum, total, last) should be used to
111 build the consolidated values (see rrdcreate). You can define
112 any number of different consolidation setups within one RRD.
113 They will all be maintained on the fly when new data is loaded
114 into the RRD.
115 Round Robin Archives
117 Data values of the same consolidation setup are stored into
118 Round Robin Archives (RRA). This is a very efficient manner to
119 store data for a certain amount of time, while using a known
120 and constant amount of storage space.
121 It works like this: If you want to store 1'000 values in 5
123 minute interval, RRDtool will allocate space for 1'000 data
124 values and a header area. In the header it will store a pointer
125 telling which slots (value) in the storage area was last
126 written to. New values are written to the Round Robin Archive
127 in, you guessed it, a round robin manner. This automatically
128 limits the history to the last 1'000 values (in our example).
129 Because you can define several RRAs within a single RRD, you
130 can setup another one, for storing 750 data values at a 2 hour
131 interval, for example, and thus keep a log for the last two
132 months at a lower resolution.
133 The use of RRAs guarantees that the RRD does not grow over time
135 and that old data is automatically eliminated. By using the
136 consolidation feature, you can still keep data for a very long
137 time, while gradually reducing the resolution of the data along
138 the time axis.
139 Using different consolidation functions (CF) allows you to
141 store exactly the type of information that actually interests
142 you: the maximum one minute traffic on the LAN, the minimum
143 temperature of your wine cellar, the total minutes of down
144 time, etc.
145 Unknown Data
147 As mentioned earlier, the RRD stores data at a constant
148 interval. Sometimes it may happen that no new data is available
149 when a value has to be written to the RRD. Data acquisition may
150 not be possible for one reason or other. With RRDtool you can
151 handle these situations by storing an *UNKNOWN* value into the
152 database. The value '*UNKNOWN*' is supported through all the
153 functions of the tool. When consolidating a data set, the
154 amount of *UNKNOWN* data values is accounted for and when a new
155 consolidated value is ready to be written to its Round Robin
156 Archive (RRA), a validity check is performed to make sure that
157 the percentage of unknown values in the data point is above a
158 configurable level. If not, an *UNKNOWN* value will be written
159 to the RRA.
160 Graphing
162 RRDtool allows you to generate reports in numerical and
163 graphical form based on the data stored in one or several RRDs.
164 The graphing feature is fully configurable. Size, color and
165 contents of the graph can be defined freely. Check rrdgraph for
166 more information on this.
167 Aberrant Behavior Detection
169 by Jake Brutlag
170 RRDtool provides the building blocks for near real-time
172 aberrant behavior detection. These components include:
173 · An algorithm for predicting the value of a time series one
175 time step into the future.
176 · A measure of deviation between predicted and observed
178 values.
179 · A mechanism to decide if and when an observed value or
181 sequence of observed values is too deviant from the
182 predicted value(s).
183 Here is a brief explanation of these components:
185 The Holt-Winters time series forecasting algorithm is an on-
187 line (or incremental) algorithm that adaptively predicts future
188 observations in a time series. Its forecast is the sum of three
189 components: a baseline (or intercept), a linear trend over time
190 (or slope), and a seasonal coefficient (a periodic effect, such
191 as a daily cycle). There is one seasonal coefficient for each
192 time point in the period (cycle). After a value is observed,
193 each of these components is updated via exponential smoothing.
194 This means that the algorithm "learns" from past values and
195 uses them to predict the future. The rate of adaptation is
196 governed by 3 parameters, alpha (intercept), beta (slope), and
197 gamma (seasonal). The prediction can also be viewed as a
198 smoothed value for the time series.
199 The measure of deviation is a seasonal weighted absolute
201 deviation. The term seasonal means deviation is measured
202 separately for each time point in the seasonal cycle. As with
203 Holt-Winters forecasting, deviation is predicted using the
204 measure computed from past values (but only at that point in
205 the seasonal cycle). After the value is observed, the algorithm
206 learns from the observed value via exponential smoothing.
207 Confidence bands for the observed time series are generated by
208 scaling the sequence of predicted deviation values (we usually
209 think of the sequence as a continuous line rather than a set of
210 discrete points).
211 Aberrant behavior (a potential failure) is reported whenever
213 the number of times the observed value violates the confidence
214 bands meets or exceeds a specified threshold within a specified
215 temporal window (e.g. 5 violations during the past 45 minutes
216 with a value observed every 5 minutes).
217 This functionality is embedded in a set of related RRAs. In
219 particular, a FAILURES RRA logs potential failures. With these
220 data you could, for example, use a front-end application to
221 RRDtool to initiate real-time alerts.
222 For a detailed description on how to set this up, see
224 rrdcreate.
225 REMOTE CONTROL
227 When you start RRDtool with the command line option '-' it waits for
228 input via standard input (STDIN). With this feature you can improve
229 performance by attaching RRDtool to another process (MRTG is one
230 example) through a set of pipes. Over these pipes RRDtool accepts the
231 same arguments as on the command line and some special commands like
232 quit, cd, mkdir and ls. For detailed help on the server commands type:
233 rrdtool help cd|mkdir|pwd|ls|quit
235 When a command is completed, RRDtool will print the string '"OK"',
237 followed by timing information of the form u:usertime s:systemtime.
238 Both values are the running totals of seconds since RRDtool was
239 started. If an error occurs, a line of the form '"ERROR:" Description
240 of error' will be printed instead. RRDtool will not abort, unless
241 something really serious happens. If a workdir is specified and the UID
242 is 0, RRDtool will do a chroot to that workdir. If the UID is not 0,
243 RRDtool only changes the current directory to workdir.
244 RRD Server
246 If you want to create a RRD-Server, you must choose a TCP/IP Service
247 number and add them to /etc/services like this:
248 rrdsrv 13900/tcp # RRD server
250 Attention: the TCP port 13900 isn't officially registered for rrdsrv.
252 You can use any unused port in your services file, but the server and
253 the client system must use the same port, of course.
254 With this configuration you can add RRDtool as meta-server to
256 /etc/inetd.conf. For example:
257 rrdsrv stream tcp nowait root /opt/rrd/bin/rrdtool rrdtool - /var/rrd
259 Don't forget to create the database directory /var/rrd and reinitialize
261 your inetd.
262 If all was setup correctly, you can access the server with Perl
264 sockets, tools like netcat, or in a quick interactive test by using
265 'telnet localhost rrdsrv'.
266 NOTE: that there is no authentication with this feature! Do not setup
268 such a port unless you are sure what you are doing.
269
271 For very big setups, updating thousands of RRD files often becomes a
272 serious IO problem. If you run into such problems, you might want to
273 take a look at rrdcached, a caching daemon for RRDtool which may help
274 you lessen the stress on your disks.
275
277 rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch, rrdtune, rrdlast,
278 rrdxport, rrdflushcached, rrdcached
279
281 Bugs? Features!
282
284 Tobias Oetiker <tobi@oetiker.ch>
2851.4.8 2013-05-23 RRDTOOL(1)