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diff --git a/doc/rrdtutorial.txt b/doc/rrdtutorial.txt
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--- a/doc/rrdtutorial.txt
+++ b/doc/rrdtutorial.txt
rrdtutorial - Alex van den Bogaerdt's RRDtool tutorial
D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
- RRDtool is written by Tobias Oetiker <tobi@oetiker.ch> with contribu-
- tions from many people all around the world. This document is written
- by Alex van den Bogaerdt <alex@vandenbogaerdt.nl> to help you under-
- stand what RRDtool is and what it can do for you.
+ RRDtool is written by Tobias Oetiker <tobi@oetiker.ch> with
+ contributions from many people all around the world. This document is
+ written by Alex van den Bogaerdt <alex@vandenbogaerdt.nl> to help you
+ understand what RRDtool is and what it can do for you.
The documentation provided with RRDtool can be too technical for some
- people. This tutorial is here to help you understand the basics of RRD-
- tool. It should prepare you to read the documentation yourself. It
- also explains the general things about statistics with a focus on net-
- working.
+ people. This tutorial is here to help you understand the basics of
+ RRDtool. It should prepare you to read the documentation yourself. It
+ also explains the general things about statistics with a focus on
+ networking.
T\bTU\bUT\bTO\bOR\bRI\bIA\bAL\bL
- I\bIm\bmp\bpo\bor\brt\bta\ban\bnt\bt
-
- Please don't skip ahead in this document! The first part of this docu-
- ment explains the basics and may be boring. But if you don't under-
- stand the basics, the examples will not be as meaningful to you.
+ I\bIm\bmp\bpo\bor\brt\bta\ban\bnt\bt
+ Please don't skip ahead in this document! The first part of this
+ document explains the basics and may be boring. But if you don't
+ understand the basics, the examples will not be as meaningful to you.
Sometimes things change. This example used to provide numbers like
"0.04" in stead of "4.00000e-02". Those are really the same numbers,
result as a fix to the source of this document. Discuss it on the
user's list, or write to me.
- W\bWh\bha\bat\bt i\bis\bs R\bRR\bRD\bDt\bto\boo\bol\bl?\b?
-
- RRDtool refers to Round Robin Database tool. Round robin is a tech-
- nique that works with a fixed amount of data, and a pointer to the cur-
- rent element. Think of a circle with some dots plotted on the edge.
+ W\bWh\bha\bat\bt i\bis\bs R\bRR\bRD\bDt\bto\boo\bol\bl?\b?
+ RRDtool refers to Round Robin Database tool. Round robin is a
+ technique that works with a fixed amount of data, and a pointer to the
+ current element. Think of a circle with some dots plotted on the edge.
These dots are the places where data can be stored. Draw an arrow from
the center of the circle to one of the dots; this is the pointer. When
- the current data is read or written, the pointer moves to the next ele-
- ment. As we are on a circle there is neither a beginning nor an end,
+ the current data is read or written, the pointer moves to the next
+ element. As we are on a circle there is neither a beginning nor an end,
you can go on and on and on. After a while, all the available places
will be used and the process automatically reuses old locations. This
- way, the dataset will not grow in size and therefore requires no main-
- tenance. RRDtool works with with Round Robin Databases (RRDs). It
+ way, the dataset will not grow in size and therefore requires no
+ maintenance. RRDtool works with with Round Robin Databases (RRDs). It
stores and retrieves data from them.
- W\bWh\bha\bat\bt d\bda\bat\bta\ba c\bca\ban\bn b\bbe\be p\bpu\but\bt i\bin\bnt\bto\bo a\ban\bn R\bRR\bRD\bD?\b?
-
+ W\bWh\bha\bat\bt d\bda\bat\bta\ba c\bca\ban\bn b\bbe\be p\bpu\but\bt i\bin\bnt\bto\bo a\ban\bn R\bRR\bRD\bD?\b?
You name it, it will probably fit as long as it is some sort of time-
series data. This means you have to be able to measure some value at
several points in time and provide this information to RRDtool. If you
can do this, RRDtool will be able to store it. The values must be
numerical but don't have to be integers, as is the case with MRTG (the
- next section will give more details on this more specialized applica-
- tion).
-
- Many examples below talk about SNMP which is an acronym for Simple Net-
- work Management Protocol. "Simple" refers to the protocol. It does not
- mean it is simple to manage or monitor a network. After working your
- way through this document, you should know enough to be able to under-
- stand what people are talking about. For now, just realize that SNMP
- can be used to query devices for the values of counters they keep. It
- is the value from those counters that we want to store in the RRD.
-
- W\bWh\bha\bat\bt c\bca\ban\bn I\bI d\bdo\bo w\bwi\bit\bth\bh t\bth\bhi\bis\bs t\bto\boo\bol\bl?\b?
-
+ next section will give more details on this more specialized
+ application).
+
+ Many examples below talk about SNMP which is an acronym for Simple
+ Network Management Protocol. "Simple" refers to the protocol. It does
+ not mean it is simple to manage or monitor a network. After working
+ your way through this document, you should know enough to be able to
+ understand what people are talking about. For now, just realize that
+ SNMP can be used to query devices for the values of counters they keep.
+ It is the value from those counters that we want to store in the RRD.
+
+ W\bWh\bha\bat\bt c\bca\ban\bn I\bI d\bdo\bo w\bwi\bit\bth\bh t\bth\bhi\bis\bs t\bto\boo\bol\bl?\b?
RRDtool originated from MRTG (Multi Router Traffic Grapher). MRTG
started as a tiny little script for graphing the use of a university's
connection to the Internet. MRTG was later (ab-)used as a tool for
- graphing other data sources including temperature, speed, voltage, num-
- ber of printouts and the like.
+ graphing other data sources including temperature, speed, voltage,
+ number of printouts and the like.
Most likely you will start to use RRDtool to store and process data
- collected via SNMP. The data will most likely be bytes (or bits) trans-
- fered from and to a network or a computer. But it can also be used to
- display tidal waves, solar radiation, power consumption, number of vis-
- itors at an exhibition, noise levels near an airport, temperature on
- your favorite holiday location, temperature in the fridge and whatever
- you imagination can come up with.
-
- You only need a sensor to measure the data and be able to feed the num-
- bers into RRDtool. RRDtool then lets you create a database, store data
- in it, retrieve that data and create graphs in PNG format for display
- on a web browser. Those PNG images are dependent on the data you col-
- lected and could be, for instance, an overview of the average network
- usage, or the peaks that occurred.
-
- W\bWh\bha\bat\bt i\bif\bf I\bI s\bst\bti\bil\bll\bl h\bha\bav\bve\be p\bpr\bro\bob\bbl\ble\bem\bms\bs a\baf\bft\bte\ber\br r\bre\bea\bad\bdi\bin\bng\bg t\bth\bhi\bis\bs d\bdo\boc\bcu\bum\bme\ben\bnt\bt?\b?
-
+ collected via SNMP. The data will most likely be bytes (or bits)
+ transfered from and to a network or a computer. But it can also be
+ used to display tidal waves, solar radiation, power consumption, number
+ of visitors at an exhibition, noise levels near an airport, temperature
+ on your favorite holiday location, temperature in the fridge and
+ whatever you imagination can come up with.
+
+ You only need a sensor to measure the data and be able to feed the
+ numbers into RRDtool. RRDtool then lets you create a database, store
+ data in it, retrieve that data and create graphs in PNG format for
+ display on a web browser. Those PNG images are dependent on the data
+ you collected and could be, for instance, an overview of the average
+ network usage, or the peaks that occurred.
+
+ W\bWh\bha\bat\bt i\bif\bf I\bI s\bst\bti\bil\bll\bl h\bha\bav\bve\be p\bpr\bro\bob\bbl\ble\bem\bms\bs a\baf\bft\bte\ber\br r\bre\bea\bad\bdi\bin\bng\bg t\bth\bhi\bis\bs d\bdo\boc\bcu\bum\bme\ben\bnt\bt?\b?
First of all: read it again! You may have missed something. If you are
unable to compile the sources and you have a fairly common OS, it will
- probably not be the fault of RRDtool. There may be pre-compiled ver-
- sions around on the Internet. If they come from trusted sources, get
+ probably not be the fault of RRDtool. There may be pre-compiled
+ versions around on the Internet. If they come from trusted sources, get
one of those.
If on the other hand the program works but does not give you the
configuration and compare it with the examples that follow.
There is a mailing list and an archive of it. Read the list for a few
- weeks and search the archive. It is considered rude to just ask a ques-
- tion without searching the archives: your problem may already have been
- solved for somebody else! This is true for most, if not all, mailing
- lists and not only for this particular one. Look in the documentation
- that came with RRDtool for the location and usage of the list.
+ weeks and search the archive. It is considered rude to just ask a
+ question without searching the archives: your problem may already have
+ been solved for somebody else! This is true for most, if not all,
+ mailing lists and not only for this particular one. Look in the
+ documentation that came with RRDtool for the location and usage of the
+ list.
I suggest you take a moment to subscribe to the mailing list right now
- by sending an email to <rrd-users-request@lists.oetiker.ch> with a sub-
- ject of "subscribe". If you ever want to leave this list, just write an
- email to the same address but now with a subject of "unsubscribe".
-
- H\bHo\bow\bw w\bwi\bil\bll\bl y\byo\bou\bu h\bhe\bel\blp\bp m\bme\be?\b?
+ by sending an email to <rrd-users-request@lists.oetiker.ch> with a
+ subject of "subscribe". If you ever want to leave this list, just write
+ an email to the same address but now with a subject of "unsubscribe".
+ H\bHo\bow\bw w\bwi\bil\bll\bl y\byo\bou\bu h\bhe\bel\blp\bp m\bme\be?\b?
By giving you some detailed descriptions with detailed examples. I
assume that following the instructions in the order presented will give
you enough knowledge of RRDtool to experiment for yourself. If it
You will need to know something about hexadecimal numbers. If you don't
then start with reading bin_dec_hex before you continue here.
- Y\bYo\bou\bur\br f\bfi\bir\brs\bst\bt R\bRo\bou\bun\bnd\bd R\bRo\bob\bbi\bin\bn D\bDa\bat\bta\bab\bba\bas\bse\be
-
+ Y\bYo\bou\bur\br f\bfi\bir\brs\bst\bt R\bRo\bou\bun\bnd\bd R\bRo\bob\bbi\bin\bn D\bDa\bat\bta\bab\bba\bas\bse\be
In my opinion the best way to learn something is to actually do it.
Why not start right now? We will create a database, put some values in
it and extract this data again. Your output should be the same as the
Assume we have a device that transfers bytes to and from the Internet.
This device keeps a counter that starts at zero when it is turned on,
- increasing with every byte that is transfered. This counter will proba-
- bly have a maximum value. If this value is reached and an extra byte is
- counted, the counter starts over at zero. This is the same as many
- counters in the world such as the mileage counter in a car.
+ increasing with every byte that is transfered. This counter will
+ probably have a maximum value. If this value is reached and an extra
+ byte is counted, the counter starts over at zero. This is the same as
+ many counters in the world such as the mileage counter in a car.
Most discussions about networking talk about bits per second so lets
get used to that right away. Assume a byte is eight bits and start to
think in bits not bytes. The counter, however, still counts bytes! In
the SNMP world most of the counters are 32 bits. That means they are
- counting from 0 to 4294967295. We will use these values in the exam-
- ples. The device, when asked, returns the current value of the
+ counting from 0 to 4294967295. We will use these values in the
+ examples. The device, when asked, returns the current value of the
counter. We know the time that has passes since we last asked so we now
know how many bytes have been transfered ***on average*** per second.
- This is not very hard to calculate. First in words, then in calcula-
- tions:
+ This is not very hard to calculate. First in words, then in
+ calculations:
1. Take the current counter, subtract the previous value from it.
- 2. Do the same with the current time and the previous time (in sec-
- onds).
+ 2. Do the same with the current time and the previous time (in
+ seconds).
3. Divide the outcome of (1) by the outcome of (2), the result is the
amount of bytes per second. Multiply by eight to get the number of
We could also calculate the speed in km/h: 12 times 5 minutes is an
hour, so we have to multiply 12 km by 12 to get 144 km/h. For our
- native English speaking friends: that's 90 mph so don't try this exam-
- ple at home or where I live :)
+ native English speaking friends: that's 90 mph so don't try this
+ example at home or where I live :)
Remember: these numbers are averages only. There is no way to figure
out from the numbers, if you drove at a constant speed. There is an
OS to OS, but I assume you can figure it out if it works different on
your's. Make sure you do not overwrite any file on your system when
executing the following command and type the whole line as one long
- line (I had to split it for readability) and skip all of the '\' char-
- acters.
+ line (I had to split it for readability) and skip all of the '\'
+ characters.
rrdtool create test.rrd \
--start 920804400 \
(So enter: "rrdtool create test.rrd --start 920804400 DS ...")
- W\bWh\bha\bat\bt h\bha\bas\bs b\bbe\bee\ben\bn c\bcr\bre\bea\bat\bte\bed\bd?\b?
-
+ W\bWh\bha\bat\bt h\bha\bas\bs b\bbe\bee\ben\bn c\bcr\bre\bea\bat\bte\bed\bd?\b?
We created the round robin database called test (test.rrd) which starts
at noon the day I started writing this document, 7th of March, 1999
(this date translates to 920804400 seconds as explained below). Our
The meaning of the above output will become clear below.
- T\bTi\bim\bme\be t\bto\bo c\bcr\bre\bea\bat\bte\be s\bso\bom\bme\be g\bgr\bra\bap\bph\bhi\bic\bcs\bs
-
+ T\bTi\bim\bme\be t\bto\bo c\bcr\bre\bea\bat\bte\be s\bso\bom\bme\be g\bgr\bra\bap\bph\bhi\bic\bcs\bs
Try the following command:
rrdtool graph speed.png \
If this has worked: congratulations! If not, check what went wrong.
- The colors are built up from red, green and blue. For each of the com-
- ponents, you specify how much to use in hexadecimal where 00 means not
- included and FF means fully included. The "color" white is a mixture
- of red, green and blue: FFFFFF The "color" black is all colors off:
- 000000
+ The colors are built up from red, green and blue. For each of the
+ components, you specify how much to use in hexadecimal where 00 means
+ not included and FF means fully included. The "color" white is a
+ mixture of red, green and blue: FFFFFF The "color" black is all colors
+ off: 000000
red #FF0000
green #00FF00
viewer. Web browsers will display the PNG via the URL
"file:///the/path/to/speed.png"
- G\bGr\bra\bap\bph\bhi\bic\bcs\bs w\bwi\bit\bth\bh s\bso\bom\bme\be m\bma\bat\bth\bh
-
+ G\bGr\bra\bap\bph\bhi\bic\bcs\bs w\bwi\bit\bth\bh s\bso\bom\bme\be m\bma\bat\bth\bh
When looking at the image, you notice that the horizontal axis is
labeled 12:10, 12:20, 12:30, 12:40 and 12:50. Sometimes a label doesn't
fit (12:00 and 13:00 would be likely candidates) so they are skipped.
If we had measured our distances in meters, this would have been
(12357000-12345000)/300 = 12000/300 = 40.
- As most people have a better feel for numbers in this range, we'll cor-
- rect that. We could recreate our database and store the correct data,
- but there is a better way: we do some calculations while creating the
- png file!
+ As most people have a better feel for numbers in this range, we'll
+ correct that. We could recreate our database and store the correct
+ data, but there is a better way: we do some calculations while creating
+ the png file!
rrdtool graph speed2.png \
--start 920804400 --end 920808000 \
detail. Also, you may want to read my tutorial on CDEFs and Steve
Rader's tutorial on RPN. But first finish this tutorial.
- Hang on! If we can multiply values with 1000, it should also be possi-
- ble to display kilometers per hour from the same data!
+ Hang on! If we can multiply values with 1000, it should also be
+ possible to display kilometers per hour from the same data!
To change a value that is measured in meters per second:
Check if kmh is greater than 100 ( kmh,100 ) GT
If so, return kmh, else return 0 ((( kmh,100) GT ), kmh, 0) IF
- G\bGr\bra\bap\bph\bhi\bic\bcs\bs M\bMa\bag\bgi\bic\bc
-
+ G\bGr\bra\bap\bph\bhi\bic\bcs\bs M\bMa\bag\bgi\bic\bc
I like to believe there are virtually no limits to how RRDtool graph
can manipulate data. I will not explain how it works, but look at the
following PNG:
not be enough, especially when proxies are involved. Try shift-reload
or ctrl-F5).
- U\bUp\bpd\bda\bat\bte\bes\bs i\bin\bn R\bRe\bea\bal\bli\bit\bty\by
-
+ U\bUp\bpd\bda\bat\bte\bes\bs i\bin\bn R\bRe\bea\bal\bli\bit\bty\by
We've already used the "update" command: it took one or more parameters
in the form of "<time>:<value>". You'll be glad to know that you can
specify the current time by filling in a "N" as the time. Or you could
- use the "time" function in Perl (the shortest example in this tuto-
- rial):
+ use the "time" function in Perl (the shortest example in this
+ tutorial):
perl -e 'print time, "\n" '
them in a script as well. After running that script, view the page
index.html we created above.
- S\bSo\bom\bme\be w\bwo\bor\brd\bds\bs o\bon\bn S\bSN\bNM\bMP\bP
-
+ S\bSo\bom\bme\be w\bwo\bor\brd\bds\bs o\bon\bn S\bSN\bNM\bMP\bP
I can imagine very few people that will be able to get real data from
their car every five minutes. All other people will have to settle for
some other kind of counter. You could measure the number of pages
- printed by a printer, for example, the cups of coffee made by the cof-
- fee machine, a device that counts the electricity used, whatever. Any
- incrementing counter can be monitored and graphed using the stuff you
- learned so far. Later on we will also be able to monitor other types of
- values like temperature.
+ printed by a printer, for example, the cups of coffee made by the
+ coffee machine, a device that counts the electricity used, whatever.
+ Any incrementing counter can be monitored and graphed using the stuff
+ you learned so far. Later on we will also be able to monitor other
+ types of values like temperature.
Many people interested in RRDtool will use the counter that keeps track
of octets (bytes) transfered by a network device. So let's do just that
next. We will start with a description of how to collect data.
Some people will make a remark that there are tools which can do this
- data collection for you. They are right! However, I feel it is impor-
- tant that you understand they are not necessary. When you have to
+ data collection for you. They are right! However, I feel it is
+ important that you understand they are not necessary. When you have to
determine why things went wrong you need to know how they work.
One tool used in the example has been talked about very briefly in the
For device you substitute the name, or the IP address, of your device.
For password you use the "community read string" as it is called in the
- SNMP world. For some devices the default of "public" might work, how-
- ever this can be disabled, altered or protected for privacy and secu-
- rity reasons. Read the documentation that comes with your device or
- program.
+ SNMP world. For some devices the default of "public" might work,
+ however this can be disabled, altered or protected for privacy and
+ security reasons. Read the documentation that comes with your device
+ or program.
- Then there is this parameter, called OID, which means "object identi-
- fier".
+ Then there is this parameter, called OID, which means "object
+ identifier".
When you start to learn about SNMP it looks very confusing. It isn't
all that difficult when you look at the Management Information Base
snmpget -v2c -c public myrouter system.sysDescr.0
The device should answer with a description of itself, perhaps an empty
- one. Until you got a valid answer from a device, perhaps using a dif-
- ferent "password", or a different device, there is no point in continu-
- ing.
+ one. Until you got a valid answer from a device, perhaps using a
+ different "password", or a different device, there is no point in
+ continuing.
snmpget -v2c -c public myrouter interfaces.ifNumber.0
interfaces.ifTable.ifEntry.ifDescr.4 = "Ethernet0"
interfaces.ifTable.ifEntry.ifDescr.5 = "Loopback0"
- On this cisco equipment, I would like to monitor the "Ethernet0" inter-
- face and from the above output I see that it is number four. I try:
+ On this cisco equipment, I would like to monitor the "Ethernet0"
+ interface and from the above output I see that it is number four. I
+ try:
[user@host /home/alex]$ snmpget -v2c -c public cisco 2.2.1.10.4 2.2.1.16.4
continue on with this tutorial. If not, then go back and re-read this
part.
- A\bA R\bRe\bea\bal\bl W\bWo\bor\brl\bld\bd E\bEx\bxa\bam\bmp\bpl\ble\be
-
+ A\bA R\bRe\bea\bal\bl W\bWo\bor\brl\bld\bd E\bEx\bxa\bam\bmp\bpl\ble\be
Let the fun begin. First, create a new database. It contains data from
two counters, called input and output. The data is put into archives
that average it. They take 1, 6, 24 or 288 samples at a time. They
732 1-day samples: 732 days
These ranges are appended, so the total amount of data stored in the
- database is approximately 797 days. RRDtool stores the data differ-
- ently, it doesn't start the "weekly" archive where the "daily" archive
- stopped. For both archives the most recent data will be near "now" and
- therefore we will need to keep more data than MRTG does!
+ database is approximately 797 days. RRDtool stores the data
+ differently, it doesn't start the "weekly" archive where the "daily"
+ archive stopped. For both archives the most recent data will be near
+ "now" and therefore we will need to keep more data than MRTG does!
We will need:
Suggestion: Display in bytes per second and in bits per second. Make
the Ethernet graphics go red if they are over four megabits per second.
- C\bCo\bon\bns\bso\bol\bli\bid\bda\bat\bti\bio\bon\bn F\bFu\bun\bnc\bct\bti\bio\bon\bns\bs
-
- A few paragraphs back I mentioned the possibility of keeping the maxi-
- mum values instead of the average values. Let's go into this a bit
+ C\bCo\bon\bns\bso\bol\bli\bid\bda\bat\bti\bio\bon\bn F\bFu\bun\bnc\bct\bti\bio\bon\bns\bs
+ A few paragraphs back I mentioned the possibility of keeping the
+ maximum values instead of the average values. Let's go into this a bit
more.
Recall all the stuff about the speed of the car. Suppose we drove at
144 km/h during 5 minutes and then were stopped by the police for 25
minutes. At the end of the lecture we would take our laptop and create
and view the image taken from the database. If we look at the second
- RRA we did create, we would have the average from 6 samples. The sam-
- ples measured would be 144+0+0+0+0+0=144, divided by 30 minutes, cor-
- rected for the error by 1000, translated into km/h, with a result of 24
- km/h. I would still get a ticket but not for speeding anymore :)
+ RRA we did create, we would have the average from 6 samples. The
+ samples measured would be 144+0+0+0+0+0=144, divided by 30 minutes,
+ corrected for the error by 1000, translated into km/h, with a result of
+ 24 km/h. I would still get a ticket but not for speeding anymore :)
Obviously, in this case we shouldn't look at the averages. In some
cases they are handy. If you want to know how many km you had traveled,
averages. If you want to know the rate, look at the maximum. Over
time, they will grow apart more and more. In the last database we have
created, there are two archives that keep data per day. The archive
- that keeps averages will show low numbers, the archive that shows max-
- ima will have higher numbers.
+ that keeps averages will show low numbers, the archive that shows
+ maxima will have higher numbers.
For my car this would translate in averages per day of 96/24=4 km/h (as
I travel about 94 kilometers on a day) during working days, and maxima
of 120 km/h (my top speed that I reach every day).
- Big difference. Do not look at the second graph to estimate the dis-
- tances that I travel and do not look at the first graph to estimate my
- speed. This will work if the samples are close together, as they are in
- five minutes, but not if you average.
+ Big difference. Do not look at the second graph to estimate the
+ distances that I travel and do not look at the first graph to estimate
+ my speed. This will work if the samples are close together, as they are
+ in five minutes, but not if you average.
On some days, I go for a long ride. If I go across Europe and travel
for 12 hours, the first graph will rise to about 60 km/h. The second
stop a few times for gas and coffee. Drive slowly through Austria and
the Netherlands. Be careful in the mountains and villages. If you would
look at the graphs created from the five-minute averages you would get
- a totally different picture. You would see the same values on the aver-
- age and maximum graphs (provided I measured every 300 seconds). You
- would be able to see when I stopped, when I was in top gear, when I
+ a totally different picture. You would see the same values on the
+ average and maximum graphs (provided I measured every 300 seconds).
+ You would be able to see when I stopped, when I was in top gear, when I
drove over fast highways etc. The granularity of the data is much
higher, so you can see more. However, this takes 12 samples per hour,
or 288 values per day, so it would be a lot of data over a longer
day. From this one value, we cannot see much detail, of course.
Make sure you understand the last few paragraphs. There is no value in
- only a line and a few axis, you need to know what they mean and inter-
- pret the data in an appropriate way. This is true for all data.
+ only a line and a few axis, you need to know what they mean and
+ interpret the data in an appropriate way. This is true for all data.
- The biggest mistake you can make is to use the collected data for some-
- thing that it is not suitable for. You would be better off if you
+ The biggest mistake you can make is to use the collected data for
+ something that it is not suitable for. You would be better off if you
didn't have the graph at all.
- L\bLe\bet\bt'\b's\bs r\bre\bev\bvi\bie\bew\bw w\bwh\bha\bat\bt y\byo\bou\bu n\bno\bow\bw s\bsh\bho\bou\bul\bld\bd k\bkn\bno\bow\bw
-
+ L\bLe\bet\bt'\b's\bs r\bre\bev\bvi\bie\bew\bw w\bwh\bha\bat\bt y\byo\bou\bu n\bno\bow\bw s\bsh\bho\bou\bul\bld\bd k\bkn\bno\bow\bw
You know how to create a database and can put data in it. You can get
the numbers out again by creating an image, do math on the data from
the database and view the result instead of the raw data. You know
not only with the rest of this tutorial, but also in your day to day
monitoring long after you read this introduction.
- D\bDa\bat\bta\ba S\bSo\bou\bur\brc\bce\be T\bTy\byp\bpe\bes\bs
-
+ D\bDa\bat\bta\ba S\bSo\bou\bur\brc\bce\be T\bTy\byp\bpe\bes\bs
All right, you feel like continuing. Welcome back and get ready for an
increased speed in the examples and explanations.
You know that in order to view a counter over time, you have to take
two numbers and divide the difference of them between the time lapsed.
- This makes sense for the examples I gave you but there are other possi-
- bilities. For instance, I'm able to retrieve the temperature from my
- router in three places namely the inlet, the so called hot-spot and the
- exhaust. These values are not counters. If I take the difference of
- the two samples and divide that by 300 seconds I would be asking for
+ This makes sense for the examples I gave you but there are other
+ possibilities. For instance, I'm able to retrieve the temperature from
+ my router in three places namely the inlet, the so called hot-spot and
+ the exhaust. These values are not counters. If I take the difference
+ of the two samples and divide that by 300 seconds I would be asking for
the temperature change per second. Hopefully this is zero! If not, the
computer room is probably on fire :)
So, what can we do? We can tell RRDtool to store the values we measure
directly as they are (this is not entirely true but close enough). The
graphs we make will look much better, they will show a rather constant
- value. I know when the router is busy (it works -> it uses more elec-
- tricity -> it generates more heat -> the temperature rises). I know
+ value. I know when the router is busy (it works -> it uses more
+ electricity -> it generates more heat -> the temperature rises). I know
when the doors are left open (the room is air conditioned) -> the warm
air from the rest of the building flows into the computer room -> the
inlet temperature rises). Etc. The data type we use when creating the
The two additional types are DERIVE and ABSOLUTE. Absolute can be used
like counter with one difference: RRDtool assumes the counter is reset
- when it's read. That is: its delta is known without calculation by RRD-
- tool whereas RRDtool needs to calculate it for the counter type. Exam-
- ple: our first example (12345, 12357, 12363, 12363) would read:
+ when it's read. That is: its delta is known without calculation by
+ RRDtool whereas RRDtool needs to calculate it for the counter type.
+ Example: our first example (12345, 12357, 12363, 12363) would read:
unknown, 12, 6, 0. The rest of the calculations stay the same. The
other one, derive, is like counter. Unlike counter, it can also
- decrease so it can have a negative delta. Again, the rest of the calcu-
- lations stay the same.
+ decrease so it can have a negative delta. Again, the rest of the
+ calculations stay the same.
Let's try them all:
DEF:linec=all.rrd:c:AVERAGE LINE3:linec#0000FF:"Line C" \
DEF:lined=all.rrd:d:AVERAGE LINE3:lined#000000:"Line D"
- R\bRR\bRD\bDt\bto\boo\bol\bl u\bun\bnd\bde\ber\br t\bth\bhe\be M\bMi\bic\bcr\bro\bos\bsc\bco\bop\bpe\be
-
-
- · Line A is a COUNTER type, so it should continuously increment and
+ R\bRR\bRD\bDt\bto\boo\bol\bl u\bun\bnd\bde\ber\br t\bth\bhe\be M\bMi\bic\bcr\bro\bos\bsc\bco\bop\bpe\be
+ · Line A is a COUNTER type, so it should continuously increment and
RRDtool must calculate the differences. Also, RRDtool needs to divide
the difference by the amount of time lapsed. This should end up as a
straight line at 1 (the deltas are 300, the time is 300).
- · Line B is of type GAUGE. These are "real" values so they should match
+ · Line B is of type GAUGE. These are "real" values so they should match
what we put in: a sort of a wave.
- · Line C is of type DERIVE. It should be a counter that can decrease.
+ · Line C is of type DERIVE. It should be a counter that can decrease.
It does so between 2400 and 0, with 1800 in-between.
- · Line D is of type ABSOLUTE. This is like counter but it works on val-
- ues without calculating the difference. The numbers are the same and
- as you can see (hopefully) this has a different result.
+ · Line D is of type ABSOLUTE. This is like counter but it works on
+ values without calculating the difference. The numbers are the same
+ and as you can see (hopefully) this has a different result.
This translates in the following values, starting at 23:10 and ending
at 00:10 the next day (where "u" means unknown/unplotted):
- Line C: u u 2 2 2 0 -2 -6 2 0 2 u
- Line D: u 1 2 3 4 5 6 7 8 9 10 u
- If your PNG shows all this, you know you have entered the data cor-
- rectly, the RRDtool executable is working properly, your viewer doesn't
- fool you, and you successfully entered the year 2000 :)
+ If your PNG shows all this, you know you have entered the data
+ correctly, the RRDtool executable is working properly, your viewer
+ doesn't fool you, and you successfully entered the year 2000 :)
You could try the same example four times, each time with only one of
the lines.
Let's go over the data again:
- · Line A: 300,600,900 and so on. The counter delta is a constant 300
+ · Line A: 300,600,900 and so on. The counter delta is a constant 300
and so is the time delta. A number divided by itself is always 1
(except when dividing by zero which is undefined/illegal).
Why is it that the first point is unknown? We do know what we put
- into the database, right? True, But we didn't have a value to calcu-
- late the delta from, so we don't know where we started. It would be
- wrong to assume we started at zero so we don't!
+ into the database, right? True, But we didn't have a value to
+ calculate the delta from, so we don't know where we started. It would
+ be wrong to assume we started at zero so we don't!
- · Line B: There is nothing to calculate. The numbers are as they are.
+ · Line B: There is nothing to calculate. The numbers are as they are.
- · Line C: Again, the start-out value is unknown. The same story is
- holds as for line A. In this case the deltas are not constant, there-
- fore the line is not either. If we would put the same numbers in the
- database as we did for line A, we would have gotten the same line.
- Unlike type counter, this type can decrease and I hope to show you
- later on why this makes a difference.
+ · Line C: Again, the start-out value is unknown. The same story is
+ holds as for line A. In this case the deltas are not constant,
+ therefore the line is not either. If we would put the same numbers in
+ the database as we did for line A, we would have gotten the same
+ line. Unlike type counter, this type can decrease and I hope to show
+ you later on why this makes a difference.
- · Line D: Here the device calculates the deltas. Therefore we DO know
+ · Line D: Here the device calculates the deltas. Therefore we DO know
the first delta and it is plotted. We had the same input as with line
A, but the meaning of this input is different and thus the line is
different. In this case the deltas increase each time with 300. The
time delta stays at a constant 300 and therefore the division of the
two gives increasing values.
- C\bCo\bou\bun\bnt\bte\ber\br W\bWr\bra\bap\bps\bs
-
+ C\bCo\bou\bun\bnt\bte\ber\br W\bWr\bra\bap\bps\bs
There are a few more basics to show. Some important options are still
to be covered and we haven't look at counter wraps yet. First the
counter wrap: In our car we notice that the counter shows 999987. We
- 32 bits: 0 .. 4294967295
- 64 bits: 0 .. 18446744073709551615
- If these numbers look strange to you, you can view them in their hex-
- adecimal form:
+ If these numbers look strange to you, you can view them in their
+ hexadecimal form:
- 32 bits: 0 .. FFFFFFFF
- 64 bits: 0 .. FFFFFFFFFFFFFFFF
There is a risk in this: suppose the large counter wrapped while adding
a huge delta, it could happen, theoretically, that adding the smaller
value would make the delta positive. In this unlikely case the results
- would not be correct. The increase should be nearly as high as the max-
- imum counter value for that to happen, so chances are you would have
+ would not be correct. The increase should be nearly as high as the
+ maximum counter value for that to happen, so chances are you would have
several other problems as well and this particular problem would not
even be worth thinking about. Even though, I did include an example, so
you can judge for yourself.
The next section gives you some numerical examples for counter-wraps.
- Try to do the calculations yourself or just believe me if your calcula-
- tor can't handle the numbers :)
+ Try to do the calculations yourself or just believe me if your
+ calculator can't handle the numbers :)
Correction numbers:
judge the graph with a healthy dose of suspicion if it seems weird to
you.
- D\bDa\bat\bta\ba R\bRe\bes\bsa\bam\bmp\bpl\bli\bin\bng\bg
-
- One important feature of RRDtool has not been explained yet: it is vir-
- tually impossible to collect data and feed it into RRDtool on exact
+ D\bDa\bat\bta\ba R\bRe\bes\bsa\bam\bmp\bpl\bli\bin\bng\bg
+ One important feature of RRDtool has not been explained yet: it is
+ virtually impossible to collect data and feed it into RRDtool on exact
intervals. RRDtool therefore interpolates the data, so they are stored
on exact intervals. If you do not know what this means or how it works,
then here's the help you seek:
LINE2:seconds#0000FF \
AREA:unknown#FF0000
- View both images together (add them to your index.html file) and com-
- pare. Both graphs should show the same, despite the input being differ-
- ent.
+ View both images together (add them to your index.html file) and
+ compare. Both graphs should show the same, despite the input being
+ different.
W\bWR\bRA\bAP\bPU\bUP\bP
It's time now to wrap up this tutorial. We covered all the basics for
- you to be able to work with RRDtool and to read the additional documen-
- tation available. There is plenty more to discover about RRDtool and
- you will find more and more uses for this package. You can easily cre-
- ate graphs using just the examples provided and using only RRDtool. You
- can also use one of the front ends to RRDtool that are available.
+ you to be able to work with RRDtool and to read the additional
+ documentation available. There is plenty more to discover about RRDtool
+ and you will find more and more uses for this package. You can easily
+ create graphs using just the examples provided and using only RRDtool.
+ You can also use one of the front ends to RRDtool that are available.
M\bMA\bAI\bIL\bLI\bIN\bNG\bGL\bLI\bIS\bST\bT
Remember to subscribe to the RRDtool mailing list. Even if you are not
RRDtool) I've learned while just reading the list without posting to
it. I did not need to ask the basic questions as they are answered in
the FAQ (read it!) and in various mails by other users. With thousands
- of users all over the world, there will always be people who ask ques-
- tions that you can answer because you read this and other documentation
- and they didn't.
+ of users all over the world, there will always be people who ask
+ questions that you can answer because you read this and other
+ documentation and they didn't.
S\bSE\bEE\bE A\bAL\bLS\bSO\bO
The RRDtool manpages
-1.3.99909060808 2009-04-09 RRDTUTORIAL(1)
+1.3.999 2009-06-01 RRDTUTORIAL(1)