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diff --git a/doc/rrdtutorial.txt b/doc/rrdtutorial.txt
index 2c250f1b148fe8797bb49f63f8a0cced855c43c7..c4abd73928bfd74466c8f73b0e6e25216c83f678 100644 (file)
--- a/doc/rrdtutorial.txt
+++ b/doc/rrdtutorial.txt
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
- maintenance. RRDtool works with with Round Robin Databases (RRDs). It
+ maintenance. RRDtool works 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?
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)
- transfered from and to a network or a computer. But it can also be
+ transferred 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.
+ whatever your 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
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
+ increasing with every byte that is transferred. 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.
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.
+ know how many bytes have been transferred ***on average*** per second.
This is not very hard to calculate. First in words, then in
calculations:
920808600: 6.6666666667e-03
920808900: 3.3333333333e-03
920809200: nan
-
- If it doesn't, something may be wrong. Perhaps your OS will print
- "NaN" in a different form. "NaN" stands for "Not A Number". If your OS
- writes "U" or "UNKN" or something similar that's okay. If something
+ 920809500: nan
+
+ Note that you might get more rows than you expect. The reason for this
+ is that you ask for a time range that ends on 920809200. The number
+ that is written behind 920809200: in the list above covers the time
+ range from 920808900 to 920809200, EXCLUDING 920809200. Hence to be on
+ the sure side, you receive the entry from 920809200 to 920809500 as
+ well since it INCLUDES 920809200. You may also see "NaN" instead of
+ "nan" this is OS dependent. "NaN" stands for "Not A Number". If your
+ OS writes "U" or "UNKN" or something similar that's okay. If something
else is wrong, it will probably be due to an error you made (assuming
that my tutorial is correct of course :-). In that case: delete the
database and try again.
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.
+ of octets (bytes) transferred 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
-1.3.8 2009-04-09 RRDTUTORIAL(1)
+1.4.8 2013-05-23 RRDTUTORIAL(1)