What is the 95th percentile?

MacServe.net measures the bandwidth used by our customers by polling our ethernet switches every 5 minutes. At each polling interval, inbound and outbound bandwidth usage for each server (or cluster of servers) connected to a given switch port is measured in bytes per second. These readings are stored in log files. Our bandwidth measurement system takes the total number of samples for a given switch port, sorts them from greatest to least bandwidth usage, then discards the upper 5 percent of these samples, (i.e. all the spikes) thus arriving at peak usage at the 95th percentile of all samples taken in a given time frame.

There is no way to convert between Megabits and Gigabytes when talking in terms of 95th percentile, because it can vary. e.g. if you trasferred 100Mb solidly for 2 days in a month and 1Mb for the rest of the time, the 95th percentile would be the full 100Mb because it exceeded 5% of the charging period. However if you transfer 100Mb solidly for 1 day in a month, and only 1Mb the rest of the time, the 95th percentile would be 1Mb (1% of the previous cost) despite using only half the data.

We take the 95th percentile reading (we capture all once a day) on your billing date and apply that number to a billing scale that is negotiated at the start of your contract with MacServe.net. Customers guaranteeing a greater base bandwidth will get a better discount rate.

For Example:

  • Your account includes 1U rack space at $75 per month
  • In a 30 day period, your 95th percentile peak usage is 444 Kbps
  • This makes your bandwidth charge $260.16
  • Your total cost for that month is then $75 (rack space) plus $260.16, (if you are in Texas, we collect sales tax on the bandwidth) for a total of $335.16

Bandwidth usage for all customers is displayed on password protected web pages, with graphical output produced by MRTG (www.mrtg.org) and Cacti.

MRTG 95th Example

If you are looking for the MRTG95 patch originally developed by Sean Adams, go here