How Bandwith Usage Graphs Are Generated
cPanel/WHM displays bandwidth usage data both graphically and
numerically. As it happens, the data displayed in these 2 formats may
differ due to the ways in which they are stored on the system.
- Bandwidth graphs are generated from usage information stored in RRDtool databases. These graphs include:
- cPanel >> Logs >> Bandwidth >> Traffic for Today graph.
- cPanel >> Logs >> Bandwidth >> Traffic for Last 7 Days graph.
- cPanel >> Logs >> Bandwidth >> Traffic for Last 12 Months graph.
- Numeric bandwidth usage information is generated from summary files. Screens displaying this bandwidth data include:
- WHM >> Account Information >> View Bandwidth Usage.
- WHM >> Account Information >> Limit Bandwidth Usage.
- cPanel >> Stats >> Monthly Bandwidth Transfer.
- cPanel >> Logs >> Bandwidth >> monthly bandwidth usage pie charts.
- cPanel >> Logs >> Bandwidth >> select the domain >> Bandwidth By Day.
(For more information about the discrepancies between bandwidth usage
numbers that cPanel/WHM generates from summary files and bandwidth usage
information generated by log processing programs such as AWStats,
Analog, and Webalizer, read our documentation about apparent bandwidth discrepancies.)
Because the numerical and graphical data are stored differently, there
may be discrepancies between the two. These discrepancies are rarely
problematic on production web servers; most often, they are visible
during testing, or on new websites or those with very little traffic.
This document aims to explain why these discrepancies arise.
Graphic data stored in RRDtool databases
RRD stands for round robin database. This method of storing bandwidth usage data was designed for use with routers. As such, RRDtool databases measure the rate at which data is transferred, rather than the amount of data transferred.
Since the measurement is stored as a rate, RRDtool needs to have
measured traffic during at least two 5-minute increments in order to
record any data in the database. If, for instance, your website
experiences 1 intense burst of traffic in isolation, that burst will not show on the bandwidth usage graphs.
Since this situation is unlikely to occur on a production web server,
the bandwidth usage graphs are still helpful for gauging traffic on
real-life servers.
Numeric data stored in summary files
Data stored in summary files are not rate-based. They are a summation
of all the data transferred during the interval in question. Unlike the
RRDtool data, summary files are text-based and increase in size as time
goes on.
cPanel/WHM uses this summarized data for its bandwidth limit
calculations. These files are not particularly useful for graphing or
generating composite information. They can, however, be used to recreate
the RRDtool databases, if required.
