@@ -53,7 +59,7 @@
This manual is an attempt to assist beginners in understanding the concepts of RRDtool. It sheds a light on differences between RRDtool and other databases. With help of an example, it explains the structure of RRDtool -database. This is followed by an overview of the ``graph'' feature of RRDtool. +database. This is followed by an overview of the "graph" feature of RRDtool. At the end, it has sample scripts that illustrate the usage/wrapping of RRDtool within Shell or Perl scripts.
@@ -76,7 +82,7 @@ an RRDtool database is determined at creation time. Imagine an RRDtool database as the perimeter of a circle. Data is added along the perimeter. When new data reaches the starting point, it overwrites existing data. This way, the size of an RRDtool database always -remains constant. The name ``Round Robin'' stems from this behavior.
+remains constant. The name "Round Robin" stems from this behavior.Other databases store the values as supplied. RRDtool can be configured to @@ -124,7 +130,7 @@ best explained with an example.
DS:mem:GAUGE:600:0:671744 \ RRA:AVERAGE:0.5:12:24 \ RRA:AVERAGE:0.5:288:31 -This example creates a database named target.rrd. Start time +
This example creates a database named target.rrd. Start time (1'023'654'125) is specified in total number of seconds since epoch (time in seconds since 01-01-1970). While updating the database, the update time is also specified. This update time MUST be large (later) @@ -211,7 +217,7 @@ sources.
Another important feature of RRDtool is its ability to create -graphs. The ``graph'' command uses the ``fetch'' command internally to +graphs. The "graph" command uses the "fetch" command internally to retrieve values from the database. With the retrieved values it draws graphs as defined by the parameters supplied on the command line. A single graph can show different DS (Data Sources) from a database. It @@ -230,14 +236,14 @@ for retrieving the values? RRDtool looks at several things when making its choice. First it makes sure that the RRA covers as much of the graphing time frame as possible. Second it looks at the resolution of the RRA compared to the resolution of the graph. It tries to find one -which has the same or higher better resolution. With the ``-r'' option +which has the same or higher better resolution. With the "-r" option you can force RRDtool to assume a different resolution than the one calculated from the pixel width of the graph.
Values of different variables can be presented in 5 different shapes in a graph - AREA, LINE1, LINE2, LINE3, and STACK. AREA is represented by a solid colored area with values as the boundary of this area. LINE1/2/3 (increasing width) are just plain lines representing -the values. STACK is also an area but it is ``stack''ed on top AREA or +the values. STACK is also an area but it is "stack"ed on top AREA or LINE1/2/3. Another important thing to note is that variables are plotted in the order they are defined in the graph command. Therefore care must be taken to define STACK only after defining AREA/LINE. It