Sum of multiple 95th sources same as aggregated value?

[technicidat]

Hi,

Can anyone tell me if, mathematically, the result of adding individual 95th percentile values of several graphs together (manually) would be the same thing as creating an aggregate graph which combines and adds these multiple sources together.

The combined graph would then have one 95th percentile line.
For billing purposes I need to know if there would be any difference between the two methods.

Thanks!

[gandalf]

That depends on the algorithm used. Two years ago, I noticed, that e.g. rrdtool 95Percentage and cacti were different. Rony is our expert concerning this matter
Reinhard

[rony]

Adding the values is not the correct method for billing purposes.

If you are billing on aggregate bandwidth, then you should create an aggregate graph and then use the aggregate Nth percentile functions.