Percentile calculation wrong

[erikklaassen]

I have a 95 percentile line in my interface outbound traffic graph. The line is at 57mbit.
When i grab the date from the database, create a graph i can see the excel graph is the same as in zabbix. But when i get the 95 percentile it's a different value, 47Mbit. My cacti also say's 47Mbit.

I grab the data from the history_unit table. In the file class.cchart.php i force zabbix to get the date from the history_unit table.

When using the trends table you don't get a real 5min avg 95 percentile value.

I am not quite a php engineer so i can't figure where it goes wrong. Is it possible the print some date from class.cchart.php on the screen or file for debugging?

using zabbix 1.8.9

[erikklaassen]

Did another calculation.

Took 1 month of data from a single item, 8739 values. Converted the bits to mbits, sorted the data and took the value at position 8303 (95th). This was 3,72Mbit where the graph in zabbix shows 4,37.

I hope someone can help

[erikklaassen]

My fault. I selected "max" instead of "avg" in the graph items. Calculation is now fine although i have to force zabbix to take the history data instead of trends.

And second. The calculation is only working with one item in a graph. When you have traffic in and out you will end up with twice as much data. The calculation the takes off twice to much data resulting in a to low 95 percentile.

I will add and a bug/feature request for that.