Capacity Planning

How much bandwidth is needed? Are servers trending towards maximum utilization? In 30 days, which interfaces will be most utilized on the network?

SevOne provides capacity projections to show you the projected values for any object and data indicator that we monitor. These tabular and graphic reports help you see the trajectory and trends of your data.

Additionally, SevOne provides a way to run Percentile Reports to give you better control of the data used for calculations. The first rule of network capacity planning is that traffic is bursty. It does not ramp up smoothly. Think of a web page, when it is loading it, it needs to be super fast.  Then for the next minute, while being read, nothing is going on.

Capacity planning by average data alone exposes you to some of this bursty data and can skew your results. If only enough bandwidth is provided to meet the 'average' demand, then when peak utilization hits, users will be very unhappy. To go back to the analogy of the web page, the page should load right away. It should not load slowly over the time it is to be viewed. If it takes a minute to load it, users will be very unhappy.

In the same time, network bandwidth requirements can't be engineered by peaks.  Most network devices will use all the bandwidth available when possible. So we need to compromise. The biggest peaks need to be eliminated, while still allowing users to have a decent response time. This is where the percentiles come in and 95th percentile is pretty widely accepted.  In some networks 98th percentile is the standard. Yet in others, 90th is what is used. 

What this means is tryng to find a point such that 95% of all samples fall underneath it. Then only in 5% of the cases is there more demand than the network can meet. During those times, there will likely still be enough capacity to operate – but at a reduced speed.