95th percentile & other basic questions

[emily2010]

Hello. 1. I am new to cacti 2. There is no one in my organization that I can ask these basic question to, so bear with me in my VERY limited understanding of what I am viewing.

My boss who knows nothing about how our current configuration of CACTI is being used seems to think that the 95th percentile billing is not working properly and I think I agree but would like some guidance of what we are looking at:

I have attached a screen shot of our 95th percentile graph.
1. How is the 95th percentile being calculated it looks to me as if it's just adding up the total in+out in bits...this certainly doesn't seem right.
2. Why in the In & Out portion does the graph show M and in the 95th Percentile ledgened it shows mbits (difference in caps vs. lower case) does the M represent Megabytes and the mbits is megabits as I think?

[rgreening]

Did you modify the templates or are you using the stock supplied template? Also, which 95% template did you choose (I believe there are 2 different ones).

I am using the bits in/out one, and it looks correct for me. Your's does not look correct, as the values represented in the graph do not reflect similar value for the 95%. I suspect if you go back and choose the other template this may start to look correct.

[emily2010]

thanks for the reply, unfortunately this was created by a predecessor so I don't know which template was used I guess I'll have to play around and figure out how to use a the correct 95% template...any suggestions ?

[toe_cutter]

First, im really no expert on Nth percentile! I just started yesterday because a colleague wanted the graphs :s

1) Look on the left side of the graph, it should give a clue to what units are used for the graph. Without looking at the graph template and what options are used its hard to tell.
Assuming your predecessor used the correct options, your graph and the 95th is calculated using megabits.

2) 'M' is mega and 'm' is milli. Again, if your predecessor did stuff right (one can manually define the power of 10 divisor), it should be correct in showing megabits. The actual 'mbit' has been manually written in the graph template, very easy to change to 'Mbit'.
Cacti uses the SI system of units for prefixes, heres a list of them: http://en.wikipedia.org/wiki/SI_prefix# ... I_prefixes

There are different ways in calculating the Nth percentile in cacti. I think your graphs are using the way called 'max' (since your maximum in/out values add up close to the 95th value). Cacti documentation states this for 'max':

Code: Select all

Calculates the Nth percentile based off the selected data source on the graph item which the variable is used, but it is important to note that it selects the higher of the values for each row in data source and then uses the resulting set to calculate the Nth percentile. Example, you have selected a interface data source for traffic_in, this will evaluate traffic_out and traffic_in for that selected data source (rrdtool file) and select the higher of the two values for each row of data. The resulting max values are used to calculate the Nth percentile value.

More types can be found listed here: http://docs.cacti.net/manual:087:6_reference.variables

[sini]

thanks for the reply, unfortunately this was created by a predecessor so I don't know which template was used I guess I'll have to play around and figure out how to use a the correct 95% template...any suggestions ?

You can easily check the template name.
Console > Graph Management > Template Name (column)

I think this is not the stock template version of 95th %. No red horizontal line and the colors are also not the default.