1RRDCREATE(1) rrdtool RRDCREATE(1)
2
6 rrdcreate - Set up a new Round Robin Database
7
9 rrdtool create filename [--start|-b start time] [--step|-s step]
10 [--no-overwrite] [DS:ds-name:DST:dst arguments] [RRA:CF:cf arguments]
11
13 The create function of RRDtool lets you set up new Round Robin Database
14 (RRD) files. The file is created at its final, full size and filled
15 with *UNKNOWN* data.
16 filename
18 The name of the RRD you want to create. RRD files should end with the
19 extension .rrd. However, RRDtool will accept any filename.
20 --start|-b start time (default: now - 10s)
22 Specifies the time in seconds since 1970-01-01 UTC when the first value
23 should be added to the RRD. RRDtool will not accept any data timed
24 before or at the time specified.
25 See also AT-STYLE TIME SPECIFICATION section in the rrdfetch
27 documentation for other ways to specify time.
28 --step|-s step (default: 300 seconds)
30 Specifies the base interval in seconds with which data will be fed into
31 the RRD.
32 --no-overwrite
34 Do not clobber an existing file of the same name.
35 DS:ds-name:DST:dst arguments
37 A single RRD can accept input from several data sources (DS), for
38 example incoming and outgoing traffic on a specific communication line.
39 With the DS configuration option you must define some basic properties
40 of each data source you want to store in the RRD.
41 ds-name is the name you will use to reference this particular data
43 source from an RRD. A ds-name must be 1 to 19 characters long in the
44 characters [a-zA-Z0-9_].
45 DST defines the Data Source Type. The remaining arguments of a data
47 source entry depend on the data source type. For GAUGE, COUNTER,
48 DERIVE, and ABSOLUTE the format for a data source entry is:
49 DS:ds-name:GAUGE | COUNTER | DERIVE | ABSOLUTE:heartbeat:min:max
51 For COMPUTE data sources, the format is:
53 DS:ds-name:COMPUTE:rpn-expression
55 In order to decide which data source type to use, review the
57 definitions that follow. Also consult the section on "HOW TO MEASURE"
58 for further insight.
59 GAUGE
61 is for things like temperatures or number of people in a room or
62 the value of a RedHat share.
63 COUNTER
65 is for continuous incrementing counters like the ifInOctets counter
66 in a router. The COUNTER data source assumes that the counter never
67 decreases, except when a counter overflows. The update function
68 takes the overflow into account. The counter is stored as a per-
69 second rate. When the counter overflows, RRDtool checks if the
70 overflow happened at the 32bit or 64bit border and acts accordingly
71 by adding an appropriate value to the result.
72 DERIVE
74 will store the derivative of the line going from the last to the
75 current value of the data source. This can be useful for gauges,
76 for example, to measure the rate of people entering or leaving a
77 room. Internally, derive works exactly like COUNTER but without
78 overflow checks. So if your counter does not reset at 32 or 64 bit
79 you might want to use DERIVE and combine it with a MIN value of 0.
80 NOTE on COUNTER vs DERIVE
82 by Don Baarda <don.baarda@baesystems.com>
84 If you cannot tolerate ever mistaking the occasional counter reset
86 for a legitimate counter wrap, and would prefer "Unknowns" for all
87 legitimate counter wraps and resets, always use DERIVE with min=0.
88 Otherwise, using COUNTER with a suitable max will return correct
89 values for all legitimate counter wraps, mark some counter resets
90 as "Unknown", but can mistake some counter resets for a legitimate
91 counter wrap.
92 For a 5 minute step and 32-bit counter, the probability of
94 mistaking a counter reset for a legitimate wrap is arguably about
95 0.8% per 1Mbps of maximum bandwidth. Note that this equates to 80%
96 for 100Mbps interfaces, so for high bandwidth interfaces and a
97 32bit counter, DERIVE with min=0 is probably preferable. If you are
98 using a 64bit counter, just about any max setting will eliminate
99 the possibility of mistaking a reset for a counter wrap.
100 ABSOLUTE
102 is for counters which get reset upon reading. This is used for fast
103 counters which tend to overflow. So instead of reading them
104 normally you reset them after every read to make sure you have a
105 maximum time available before the next overflow. Another usage is
106 for things you count like number of messages since the last update.
107 COMPUTE
109 is for storing the result of a formula applied to other data
110 sources in the RRD. This data source is not supplied a value on
111 update, but rather its Primary Data Points (PDPs) are computed from
112 the PDPs of the data sources according to the rpn-expression that
113 defines the formula. Consolidation functions are then applied
114 normally to the PDPs of the COMPUTE data source (that is the rpn-
115 expression is only applied to generate PDPs). In database software,
116 such data sets are referred to as "virtual" or "computed" columns.
117 heartbeat defines the maximum number of seconds that may pass between
119 two updates of this data source before the value of the data source is
120 assumed to be *UNKNOWN*.
121 min and max define the expected range values for data supplied by a
123 data source. If min and/or max are specified any value outside the
124 defined range will be regarded as *UNKNOWN*. If you do not know or care
125 about min and max, set them to U for unknown. Note that min and max
126 always refer to the processed values of the DS. For a traffic-COUNTER
127 type DS this would be the maximum and minimum data-rate expected from
128 the device.
129 If information on minimal/maximal expected values is available, always
131 set the min and/or max properties. This will help RRDtool in doing a
132 simple sanity check on the data supplied when running update.
133 rpn-expression defines the formula used to compute the PDPs of a
135 COMPUTE data source from other data sources in the same <RRD>. It is
136 similar to defining a CDEF argument for the graph command. Please refer
137 to that manual page for a list and description of RPN operations
138 supported. For COMPUTE data sources, the following RPN operations are
139 not supported: COUNT, PREV, TIME, and LTIME. In addition, in defining
140 the RPN expression, the COMPUTE data source may only refer to the names
141 of data source listed previously in the create command. This is similar
142 to the restriction that CDEFs must refer only to DEFs and CDEFs
143 previously defined in the same graph command.
144 RRA:CF:cf arguments
146 The purpose of an RRD is to store data in the round robin archives
147 (RRA). An archive consists of a number of data values or statistics for
148 each of the defined data-sources (DS) and is defined with an RRA line.
149 When data is entered into an RRD, it is first fit into time slots of
151 the length defined with the -s option, thus becoming a primary data
152 point.
153 The data is also processed with the consolidation function (CF) of the
155 archive. There are several consolidation functions that consolidate
156 primary data points via an aggregate function: AVERAGE, MIN, MAX, LAST.
157 AVERAGE
159 the average of the data points is stored.
160 MIN the smallest of the data points is stored.
162 MAX the largest of the data points is stored.
164 LAST
166 the last data points is used.
167 Note that data aggregation inevitably leads to loss of precision and
169 information. The trick is to pick the aggregate function such that the
170 interesting properties of your data is kept across the aggregation
171 process.
172 The format of RRA line for these consolidation functions is:
174 RRA:AVERAGE | MIN | MAX | LAST:xff:steps:rows
176 xff The xfiles factor defines what part of a consolidation interval may
178 be made up from *UNKNOWN* data while the consolidated value is still
179 regarded as known. It is given as the ratio of allowed *UNKNOWN* PDPs
180 to the number of PDPs in the interval. Thus, it ranges from 0 to 1
181 (exclusive).
182 steps defines how many of these primary data points are used to build a
184 consolidated data point which then goes into the archive.
185 rows defines how many generations of data values are kept in an RRA.
187 Obviously, this has to be greater than zero.
188
190 In addition to the aggregate functions, there are a set of specialized
191 functions that enable RRDtool to provide data smoothing (via the Holt-
192 Winters forecasting algorithm), confidence bands, and the flagging
193 aberrant behavior in the data source time series:
194 · RRA:HWPREDICT:rows:alpha:beta:seasonal period[:rra-num]
196 · RRA:MHWPREDICT:rows:alpha:beta:seasonal period[:rra-num]
198 · RRA:SEASONAL:seasonal period:gamma:rra-
200 num[:smoothing-window=fraction]
201 · RRA:DEVSEASONAL:seasonal period:gamma:rra-
203 num[:smoothing-window=fraction]
204 · RRA:DEVPREDICT:rows:rra-num
206 · RRA:FAILURES:rows:threshold:window length:rra-num
208 These RRAs differ from the true consolidation functions in several
210 ways. First, each of the RRAs is updated once for every primary data
211 point. Second, these RRAs are interdependent. To generate real-time
212 confidence bounds, a matched set of SEASONAL, DEVSEASONAL, DEVPREDICT,
213 and either HWPREDICT or MHWPREDICT must exist. Generating smoothed
214 values of the primary data points requires a SEASONAL RRA and either an
215 HWPREDICT or MHWPREDICT RRA. Aberrant behavior detection requires
216 FAILURES, DEVSEASONAL, SEASONAL, and either HWPREDICT or MHWPREDICT.
217 The predicted, or smoothed, values are stored in the HWPREDICT or
219 MHWPREDICT RRA. HWPREDICT and MHWPREDICT are actually two variations on
220 the Holt-Winters method. They are interchangeable. Both attempt to
221 decompose data into three components: a baseline, a trend, and a
222 seasonal coefficient. HWPREDICT adds its seasonal coefficient to the
223 baseline to form a prediction, whereas MHWPREDICT multiplies its
224 seasonal coefficient by the baseline to form a prediction. The
225 difference is noticeable when the baseline changes significantly in the
226 course of a season; HWPREDICT will predict the seasonality to stay
227 constant as the baseline changes, but MHWPREDICT will predict the
228 seasonality to grow or shrink in proportion to the baseline. The proper
229 choice of method depends on the thing being modeled. For simplicity,
230 the rest of this discussion will refer to HWPREDICT, but MHWPREDICT may
231 be substituted in its place.
232 The predicted deviations are stored in DEVPREDICT (think a standard
234 deviation which can be scaled to yield a confidence band). The FAILURES
235 RRA stores binary indicators. A 1 marks the indexed observation as
236 failure; that is, the number of confidence bounds violations in the
237 preceding window of observations met or exceeded a specified threshold.
238 An example of using these RRAs to graph confidence bounds and failures
239 appears in rrdgraph.
240 The SEASONAL and DEVSEASONAL RRAs store the seasonal coefficients for
242 the Holt-Winters forecasting algorithm and the seasonal deviations,
243 respectively. There is one entry per observation time point in the
244 seasonal cycle. For example, if primary data points are generated every
245 five minutes and the seasonal cycle is 1 day, both SEASONAL and
246 DEVSEASONAL will have 288 rows.
247 In order to simplify the creation for the novice user, in addition to
249 supporting explicit creation of the HWPREDICT, SEASONAL, DEVPREDICT,
250 DEVSEASONAL, and FAILURES RRAs, the RRDtool create command supports
251 implicit creation of the other four when HWPREDICT is specified alone
252 and the final argument rra-num is omitted.
253 rows specifies the length of the RRA prior to wrap around. Remember
255 that there is a one-to-one correspondence between primary data points
256 and entries in these RRAs. For the HWPREDICT CF, rows should be larger
257 than the seasonal period. If the DEVPREDICT RRA is implicitly created,
258 the default number of rows is the same as the HWPREDICT rows argument.
259 If the FAILURES RRA is implicitly created, rows will be set to the
260 seasonal period argument of the HWPREDICT RRA. Of course, the RRDtool
261 resize command is available if these defaults are not sufficient and
262 the creator wishes to avoid explicit creations of the other specialized
263 function RRAs.
264 seasonal period specifies the number of primary data points in a
266 seasonal cycle. If SEASONAL and DEVSEASONAL are implicitly created,
267 this argument for those RRAs is set automatically to the value
268 specified by HWPREDICT. If they are explicitly created, the creator
269 should verify that all three seasonal period arguments agree.
270 alpha is the adaption parameter of the intercept (or baseline)
272 coefficient in the Holt-Winters forecasting algorithm. See rrdtool for
273 a description of this algorithm. alpha must lie between 0 and 1. A
274 value closer to 1 means that more recent observations carry greater
275 weight in predicting the baseline component of the forecast. A value
276 closer to 0 means that past history carries greater weight in
277 predicting the baseline component.
278 beta is the adaption parameter of the slope (or linear trend)
280 coefficient in the Holt-Winters forecasting algorithm. beta must lie
281 between 0 and 1 and plays the same role as alpha with respect to the
282 predicted linear trend.
283 gamma is the adaption parameter of the seasonal coefficients in the
285 Holt-Winters forecasting algorithm (HWPREDICT) or the adaption
286 parameter in the exponential smoothing update of the seasonal
287 deviations. It must lie between 0 and 1. If the SEASONAL and
288 DEVSEASONAL RRAs are created implicitly, they will both have the same
289 value for gamma: the value specified for the HWPREDICT alpha argument.
290 Note that because there is one seasonal coefficient (or deviation) for
291 each time point during the seasonal cycle, the adaptation rate is much
292 slower than the baseline. Each seasonal coefficient is only updated (or
293 adapts) when the observed value occurs at the offset in the seasonal
294 cycle corresponding to that coefficient.
295 If SEASONAL and DEVSEASONAL RRAs are created explicitly, gamma need not
297 be the same for both. Note that gamma can also be changed via the
298 RRDtool tune command.
299 smoothing-window specifies the fraction of a season that should be
301 averaged around each point. By default, the value of smoothing-window
302 is 0.05, which means each value in SEASONAL and DEVSEASONAL will be
303 occasionally replaced by averaging it with its (seasonal period*0.05)
304 nearest neighbors. Setting smoothing-window to zero will disable the
305 running-average smoother altogether.
306 rra-num provides the links between related RRAs. If HWPREDICT is
308 specified alone and the other RRAs are created implicitly, then there
309 is no need to worry about this argument. If RRAs are created
310 explicitly, then carefully pay attention to this argument. For each RRA
311 which includes this argument, there is a dependency between that RRA
312 and another RRA. The rra-num argument is the 1-based index in the order
313 of RRA creation (that is, the order they appear in the create command).
314 The dependent RRA for each RRA requiring the rra-num argument is listed
315 here:
316 · HWPREDICT rra-num is the index of the SEASONAL RRA.
318 · SEASONAL rra-num is the index of the HWPREDICT RRA.
320 · DEVPREDICT rra-num is the index of the DEVSEASONAL RRA.
322 · DEVSEASONAL rra-num is the index of the HWPREDICT RRA.
324 · FAILURES rra-num is the index of the DEVSEASONAL RRA.
326 threshold is the minimum number of violations (observed values outside
328 the confidence bounds) within a window that constitutes a failure. If
329 the FAILURES RRA is implicitly created, the default value is 7.
330 window length is the number of time points in the window. Specify an
332 integer greater than or equal to the threshold and less than or equal
333 to 28. The time interval this window represents depends on the
334 interval between primary data points. If the FAILURES RRA is implicitly
335 created, the default value is 9.
336
338 Here is an explanation by Don Baarda on the inner workings of RRDtool.
339 It may help you to sort out why all this *UNKNOWN* data is popping up
340 in your databases:
341 RRDtool gets fed samples/updates at arbitrary times. From these it
343 builds Primary Data Points (PDPs) on every "step" interval. The PDPs
344 are then accumulated into the RRAs.
345 The "heartbeat" defines the maximum acceptable interval between
347 samples/updates. If the interval between samples is less than
348 "heartbeat", then an average rate is calculated and applied for that
349 interval. If the interval between samples is longer than "heartbeat",
350 then that entire interval is considered "unknown". Note that there are
351 other things that can make a sample interval "unknown", such as the
352 rate exceeding limits, or a sample that was explicitly marked as
353 unknown.
354 The known rates during a PDP's "step" interval are used to calculate an
356 average rate for that PDP. If the total "unknown" time accounts for
357 more than half the "step", the entire PDP is marked as "unknown". This
358 means that a mixture of known and "unknown" sample times in a single
359 PDP "step" may or may not add up to enough "known" time to warrant a
360 known PDP.
361 The "heartbeat" can be short (unusual) or long (typical) relative to
363 the "step" interval between PDPs. A short "heartbeat" means you require
364 multiple samples per PDP, and if you don't get them mark the PDP
365 unknown. A long heartbeat can span multiple "steps", which means it is
366 acceptable to have multiple PDPs calculated from a single sample. An
367 extreme example of this might be a "step" of 5 minutes and a
368 "heartbeat" of one day, in which case a single sample every day will
369 result in all the PDPs for that entire day period being set to the same
370 average rate. -- Don Baarda <don.baarda@baesystems.com>
371 time|
373 axis|
374 begin__|00|
375 |01|
376 u|02|----* sample1, restart "hb"-timer
377 u|03| /
378 u|04| /
379 u|05| /
380 u|06|/ "hbt" expired
381 u|07|
382 |08|----* sample2, restart "hb"
383 |09| /
384 |10| /
385 u|11|----* sample3, restart "hb"
386 u|12| /
387 u|13| /
388 step1_u|14| /
389 u|15|/ "swt" expired
390 u|16|
391 |17|----* sample4, restart "hb", create "pdp" for step1 =
392 |18| / = unknown due to 10 "u" labled secs > 0.5 * step
393 |19| /
394 |20| /
395 |21|----* sample5, restart "hb"
396 |22| /
397 |23| /
398 |24|----* sample6, restart "hb"
399 |25| /
400 |26| /
401 |27|----* sample7, restart "hb"
402 step2__|28| /
403 |22| /
404 |23|----* sample8, restart "hb", create "pdp" for step1, create "cdp"
405 |24| /
406 |25| /
407 graphics by vladimir.lavrov@desy.de.
409
411 Here are a few hints on how to measure:
412 Temperature
414 Usually you have some type of meter you can read to get the
415 temperature. The temperature is not really connected with a time.
416 The only connection is that the temperature reading happened at a
417 certain time. You can use the GAUGE data source type for this.
418 RRDtool will then record your reading together with the time.
419 Mail Messages
421 Assume you have a method to count the number of messages
422 transported by your mail server in a certain amount of time, giving
423 you data like '5 messages in the last 65 seconds'. If you look at
424 the count of 5 like an ABSOLUTE data type you can simply update the
425 RRD with the number 5 and the end time of your monitoring period.
426 RRDtool will then record the number of messages per second. If at
427 some later stage you want to know the number of messages
428 transported in a day, you can get the average messages per second
429 from RRDtool for the day in question and multiply this number with
430 the number of seconds in a day. Because all math is run with
431 Doubles, the precision should be acceptable.
432 It's always a Rate
434 RRDtool stores rates in amount/second for COUNTER, DERIVE and
435 ABSOLUTE data. When you plot the data, you will get on the y axis
436 amount/second which you might be tempted to convert to an absolute
437 amount by multiplying by the delta-time between the points. RRDtool
438 plots continuous data, and as such is not appropriate for plotting
439 absolute amounts as for example "total bytes" sent and received in
440 a router. What you probably want is plot rates that you can scale
441 to bytes/hour, for example, or plot absolute amounts with another
442 tool that draws bar-plots, where the delta-time is clear on the
443 plot for each point (such that when you read the graph you see for
444 example GB on the y axis, days on the x axis and one bar for each
445 day).
446
448 rrdtool create temperature.rrd --step 300 \
449 DS:temp:GAUGE:600:-273:5000 \
450 RRA:AVERAGE:0.5:1:1200 \
451 RRA:MIN:0.5:12:2400 \
452 RRA:MAX:0.5:12:2400 \
453 RRA:AVERAGE:0.5:12:2400
454 This sets up an RRD called temperature.rrd which accepts one
456 temperature value every 300 seconds. If no new data is supplied for
457 more than 600 seconds, the temperature becomes *UNKNOWN*. The minimum
458 acceptable value is -273 and the maximum is 5'000.
459 A few archive areas are also defined. The first stores the temperatures
461 supplied for 100 hours (1'200 * 300 seconds = 100 hours). The second
462 RRA stores the minimum temperature recorded over every hour (12 * 300
463 seconds = 1 hour), for 100 days (2'400 hours). The third and the fourth
464 RRA's do the same for the maximum and average temperature,
465 respectively.
466
468 rrdtool create monitor.rrd --step 300 \
469 DS:ifOutOctets:COUNTER:1800:0:4294967295 \
470 RRA:AVERAGE:0.5:1:2016 \
471 RRA:HWPREDICT:1440:0.1:0.0035:288
472 This example is a monitor of a router interface. The first RRA tracks
474 the traffic flow in octets; the second RRA generates the specialized
475 functions RRAs for aberrant behavior detection. Note that the rra-num
476 argument of HWPREDICT is missing, so the other RRAs will implicitly be
477 created with default parameter values. In this example, the forecasting
478 algorithm baseline adapts quickly; in fact the most recent one hour of
479 observations (each at 5 minute intervals) accounts for 75% of the
480 baseline prediction. The linear trend forecast adapts much more slowly.
481 Observations made during the last day (at 288 observations per day)
482 account for only 65% of the predicted linear trend. Note: these
483 computations rely on an exponential smoothing formula described in the
484 LISA 2000 paper.
485 The seasonal cycle is one day (288 data points at 300 second
487 intervals), and the seasonal adaption parameter will be set to 0.1. The
488 RRD file will store 5 days (1'440 data points) of forecasts and
489 deviation predictions before wrap around. The file will store 1 day (a
490 seasonal cycle) of 0-1 indicators in the FAILURES RRA.
491 The same RRD file and RRAs are created with the following command,
493 which explicitly creates all specialized function RRAs.
494 rrdtool create monitor.rrd --step 300 \
496 DS:ifOutOctets:COUNTER:1800:0:4294967295 \
497 RRA:AVERAGE:0.5:1:2016 \
498 RRA:HWPREDICT:1440:0.1:0.0035:288:3 \
499 RRA:SEASONAL:288:0.1:2 \
500 RRA:DEVPREDICT:1440:5 \
501 RRA:DEVSEASONAL:288:0.1:2 \
502 RRA:FAILURES:288:7:9:5
503 Of course, explicit creation need not replicate implicit create, a
505 number of arguments could be changed.
506
508 rrdtool create proxy.rrd --step 300 \
509 DS:Total:DERIVE:1800:0:U \
510 DS:Duration:DERIVE:1800:0:U \
511 DS:AvgReqDur:COMPUTE:Duration,Requests,0,EQ,1,Requests,IF,/ \
512 RRA:AVERAGE:0.5:1:2016
513 This example is monitoring the average request duration during each 300
515 sec interval for requests processed by a web proxy during the interval.
516 In this case, the proxy exposes two counters, the number of requests
517 processed since boot and the total cumulative duration of all processed
518 requests. Clearly these counters both have some rollover point, but
519 using the DERIVE data source also handles the reset that occurs when
520 the web proxy is stopped and restarted.
521 In the RRD, the first data source stores the requests per second rate
523 during the interval. The second data source stores the total duration
524 of all requests processed during the interval divided by 300. The
525 COMPUTE data source divides each PDP of the AccumDuration by the
526 corresponding PDP of TotalRequests and stores the average request
527 duration. The remainder of the RPN expression handles the divide by
528 zero case.
529
531 Tobias Oetiker <tobi@oetiker.ch>
5321.4.8 2013-05-23 RRDCREATE(1)