1RRDTOOL(1) rrdtool RRDTOOL(1)
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6 rrdtool - Round Robin Database Tool
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9 rrdtool - [workdir]| function
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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 dump Dump the contents of an RRD in plain ASCII. In connection with
52 restore you can use this to move an RRD from one computer
53 architecture to another. Check rrddump.
54 restore Restore an RRD in XML format to a binary RRD. Check rrdrestore
56 fetch Get data for a certain time period from a RRD. The graph
58 function uses fetch to retrieve its data from an RRD. Check
59 rrdfetch.
60 tune Alter setup of an RRD. Check rrdtune.
62 last Find the last update time of an RRD. Check rrdlast.
64 info Get information about an RRD. Check rrdinfo.
66 rrdresize
68 Change the size of individual RRAs. This is dangerous! Check
69 rrdresize.
70 xport Export data retrieved from one or several RRDs. Check rrdxport
72 rrdcgi This is a standalone tool for producing RRD graphs on the fly.
74 Check rrdcgi.
75 HOW DOES RRDTOOL WORK?
77 Data Acquisition
78 When monitoring the state of a system, it is convenient to have
79 the data available at a constant time interval. Unfortunately,
80 you may not always be able to fetch data at exactly the time
81 you want to. Therefore RRDtool lets you update the logfile at
82 any time you want. It will automatically interpolate the value
83 of the data-source (DS) at the latest official time-slot
84 (interval) and write this interpolated value to the log. The
85 original value you have supplied is stored as well and is also
86 taken into account when interpolating the next log entry.
87 Consolidation
89 You may log data at a 1 minute interval, but you might also be
90 interested to know the development of the data over the last
91 year. You could do this by simply storing the data in 1 minute
92 intervals for the whole year. While this would take
93 considerable disk space it would also take a lot of time to
94 analyze the data when you wanted to create a graph covering the
95 whole year. RRDtool offers a solution to this problem through
96 its data consolidation feature. When setting up an Round Robin
97 Database (RRD), you can define at which interval this
98 consolidation should occur, and what consolidation function
99 (CF) (average, minimum, maximum, total, last) should be used to
100 build the consolidated values (see rrdcreate). You can define
101 any number of different consolidation setups within one RRD.
102 They will all be maintained on the fly when new data is loaded
103 into the RRD.
104 Round Robin Archives
106 Data values of the same consolidation setup are stored into
107 Round Robin Archives (RRA). This is a very efficient manner to
108 store data for a certain amount of time, while using a known
109 and constant amount of storage space.
110 It works like this: If you want to store 1'000 values in 5
112 minute interval, RRDtool will allocate space for 1'000 data
113 values and a header area. In the header it will store a pointer
114 telling which slots (value) in the storage area was last
115 written to. New values are written to the Round Robin Archive
116 in, you guessed it, a round robin manner. This automatically
117 limits the history to the last 1'000 values (in our example).
118 Because you can define several RRAs within a single RRD, you
119 can setup another one, for storing 750 data values at a 2 hour
120 interval, for example, and thus keep a log for the last two
121 months at a lower resolution.
122 The use of RRAs guarantees that the RRD does not grow over time
124 and that old data is automatically eliminated. By using the
125 consolidation feature, you can still keep data for a very long
126 time, while gradually reducing the resolution of the data along
127 the time axis.
128 Using different consolidation functions (CF) allows you to
130 store exactly the type of information that actually interests
131 you: the maximum one minute traffic on the LAN, the minimum
132 temperature of your wine cellar, the total minutes of down
133 time, etc.
134 Unknown Data
136 As mentioned earlier, the RRD stores data at a constant
137 interval. Sometimes it may happen that no new data is available
138 when a value has to be written to the RRD. Data acquisition may
139 not be possible for one reason or other. With RRDtool you can
140 handle these situations by storing an *UNKNOWN* value into the
141 database. The value '*UNKNOWN*' is supported through all the
142 functions of the tool. When consolidating a data set, the
143 amount of *UNKNOWN* data values is accounted for and when a new
144 consolidated value is ready to be written to its Round Robin
145 Archive (RRA), a validity check is performed to make sure that
146 the percentage of unknown values in the data point is above a
147 configurable level. If not, an *UNKNOWN* value will be written
148 to the RRA.
149 Graphing
151 RRDtool allows you to generate reports in numerical and
152 graphical form based on the data stored in one or several RRDs.
153 The graphing feature is fully configurable. Size, color and
154 contents of the graph can be defined freely. Check rrdgraph for
155 more information on this.
156 Aberrant Behavior Detection
158 by Jake Brutlag
159 RRDtool provides the building blocks for near real-time
161 aberrant behavior detection. These components include:
162 · An algorithm for predicting the value of a time series one
164 time step into the future.
165 · A measure of deviation between predicted and observed
167 values.
168 · A mechanism to decide if and when an observed value or
170 sequence of observed values is too deviant from the
171 predicted value(s).
172 Here is a brief explanation of these components:
174 The Holt-Winters time series forecasting algorithm is an on-
176 line (or incremental) algorithm that adaptively predicts future
177 observations in a time series. Its forecast is the sum of three
178 components: a baseline (or intercept), a linear trend over time
179 (or slope), and a seasonal coefficient (a periodic effect, such
180 as a daily cycle). There is one seasonal coefficient for each
181 time point in the period (cycle). After a value is observed,
182 each of these components is updated via exponential smoothing.
183 This means that the algorithm "learns" from past values and
184 uses them to predict the future. The rate of adaptation is
185 governed by 3 parameters, alpha (intercept), beta (slope), and
186 gamma (seasonal). The prediction can also be viewed as a
187 smoothed value for the time series.
188 The measure of deviation is a seasonal weighted absolute
190 deviation. The term seasonal means deviation is measured
191 separately for each time point in the seasonal cycle. As with
192 Holt-Winters forecasting, deviation is predicted using the
193 measure computed from past values (but only at that point in
194 the seasonal cycle). After the value is observed, the algorithm
195 learns from the observed value via exponential smoothing.
196 Confidence bands for the observed time series are generated by
197 scaling the sequence of predicted deviation values (we usually
198 think of the sequence as a continuous line rather than a set of
199 discrete points).
200 Aberrant behavior (a potential failure) is reported whenever
202 the number of times the observed value violates the confidence
203 bands meets or exceeds a specified threshold within a specified
204 temporal window (e.g. 5 violations during the past 45 minutes
205 with a value observed every 5 minutes).
206 This functionality is embedded in a set of related RRAs. In
208 particular, a FAILURES RRA logs potential failures. With these
209 data you could, for example, use a front-end application to
210 RRDtool to initiate real-time alerts.
211 For a detailed description on how to set this up, see
213 rrdcreate.
214 REMOTE CONTROL
216 When you start RRDtool with the command line option '-' it waits for
217 input via standard input (STDIN). With this feature you can improve
218 performance by attaching RRDtool to another process (MRTG is one
219 example) through a set of pipes. Over these pipes RRDtool accepts the
220 same arguments as on the command line and some special commands like
221 quit, cd, mkdir and ls. For detailed help on the server commands type:
222 rrdtool help cd|mkdir|pwd|ls|quit
224 When a command is completed, RRDtool will print the string '"OK"',
226 followed by timing information of the form u:usertime s:systemtime.
227 Both values are the running totals of seconds since RRDtool was
228 started. If an error occurs, a line of the form '"ERROR:" Description
229 of error' will be printed instead. RRDtool will not abort, unless
230 something really serious happens. If a workdir is specified and the UID
231 is 0, RRDtool will do a chroot to that workdir. If the UID is not 0,
232 RRDtool only changes the current directory to workdir.
233 RRD Server
235 If you want to create a RRD-Server, you must choose a TCP/IP Service
236 number and add them to /etc/services like this:
237 rrdsrv 13900/tcp # RRD server
239 Attention: the TCP port 13900 isn't officially registered for rrdsrv.
241 You can use any unused port in your services file, but the server and
242 the client system must use the same port, of course.
243 With this configuration you can add RRDtool as meta-server to
245 /etc/inetd.conf. For example:
246 rrdsrv stream tcp nowait root /opt/rrd/bin/rrdtool rrdtool - /var/rrd
248 Don't forget to create the database directory /var/rrd and reinitialize
250 your inetd.
251 If all was setup correctly, you can access the server with Perl
253 sockets, tools like netcat, or in a quick interactive test by using
254 'telnet localhost rrdsrv'.
255 NOTE: that there is no authentication with this feature! Do not setup
257 such a port unless you are sure what you are doing.
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260 rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch, rrdtune, rrdlast,
261 rrdxport
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264 Bugs? Features!
265
267 Tobias Oetiker <tobi@oetiker.ch>
2681.3.8 2008-12-22 RRDTOOL(1)