RRDTOOL(1) rrdtool RRDTOOL(1)
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rrdtool - round robin database tool
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rrrrrrrrddddttttoooooooollll ---- | _f_u_n_c_t_i_o_n
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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 rrrrrrrrddddttttoooooooollll kicks in. It lets you _l_o_g _a_n_d
_a_n_a_l_y_z_e the data you gather from all kinds of data-sources
(DDDDSSSS). 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 rrrrrrrrddddttttoooooooollll check the corre
sponding man page.
For an introduction to the usage of rrdtool make sure you
check the rrdtutorial manpage.
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While the man pages talk of command line switches you have
to set in order to make rrrrrrrrddddttttoooooooollll work it is important to
note that the rrrrrrrrddddttttoooooooollll can be 'remote controlled' through a
set of pipes. This saves a considerable amount of startup
time when you plan to make rrrrrrrrddddttttoooooooollll 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, ...
ccccrrrreeeeaaaatttteeee Set up a new Round Robin Database (RRD). Check the
rrdcreate manpage.
uuuuppppddddaaaatttteeee Store new data values into an RRD. Check the
rrdupdate manpage.
ggggrrrraaaapppphhhh 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.
dddduuuummmmpppp 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.
rrrreeeessssttttoooorrrreeee Restore an RRD in XML format to a binary rrd ...
Check the rrdrestore manpage
ffffeeeettttcccchhhh 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.
ttttuuuunnnneeee Alter setup of an RRD. Check the rrdtune manpage.
llllaaaasssstttt Find last update time of an RRD. Check the rrdlast
manpage.
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Change the size of individual RRAs ... Dangerous!
Check the rrdresize manpage.
rrrrrrrrddddccccggggiiii This is a standalone tool for producing rrd graphs
on the fly. Check the rrdcgi manpage.
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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 rrrrrrrrddddttttoooooooollll lets you update the logfile at
any time you want. It will automatically interpo
late the value of the data-source (DDDDSSSS) 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. rrrrrrrrddddttttoooooooollll offers a solution to
this of this problem through its data consolida
tion feature. When setting up an Round Robin
Database (RRRRRRRRDDDD), you can define at which interval
this consolidation should occur, and what consoli
dation function (CCCCFFFF) (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 RRRRRRRRDDDD. They will all be maintained on the fly
when new data is loaded into the RRRRRRRRDDDD.
Round Robin Archives
Data values of the same consolidation setup are
stored into Round Robin Archives (RRRRRRRRAAAA). 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, rrrrrrrrddddttttoooooooollll 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 RRRRRRRRAAAAs within a single RRRRRRRRDDDD, 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 RRRRRRRRAAAAs guarantees that the RRRRRRRRDDDD 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 (CCCCFFFF) 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 RRRRRRRRDDDD 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 RRRRRRRRDDDD. Data acquisition may not be possible
for one reason or an other. The rrrrrrrrddddttttoooooooollll handles
these situations by storing an _*_U_N_K_N_O_W_N_* value
into the database. The value '_*_U_N_K_N_O_W_N_*' is sup
ported through all the functions of the database.
When consolidating the amount of _*_U_N_K_N_O_W_N_* data is
accumulated and when a new consolidated value is
ready to be written to its Round Robin Archive
(RRRRRRRRAAAA) 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
_*_U_N_K_N_O_W_N_* value will be written to the RRRRRRRRAAAA.
Graphing
The rrrrrrrrddddttttoooooooollll also allows one to generate reports in
numerical and graphical form based on the data
stored in one or several RRRRRRRRDDDDs. 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.
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When you start rrrrrrrrddddttttoooooooollll with the command line option '----',
it waits for input via standard in. With this feature you
can improve performance by attaching rrrrrrrrddddttttoooooooollll to another
process (mrtg is one example) through a set of pipes. Over
the pipes rrrrrrrrddddttttoooooooollll 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 uuuu::::_u_s_e_r_t_i_m_e ssss::::_s_y_s_t_e_m_t_i_m_e both values are run
ning totals of seconds since rrdtool was started. If an
error occurs, a line of the form '"ERROR:" _D_e_s_c_r_i_p_t_i_o_n _o_f
_e_r_r_o_r' will be printed. rrrrrrrrddddttttoooooooollll will not abort if possi
ble, but follow the ERROR line with an OK line.
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rrdcreate, rrdupdate, rrdgraph, rrddump, rrdfetch, rrd
tune, rrdlast
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Bugs ? Features !
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Tobias Oetiker <oetiker@ee.ethz.ch>
