Exported Report – Custom Disk Capacity Forecast

SolarWinds Orion Capacity Forecast allows us to see trends and to find out when the capacity of the devices will be fully used. One of the sections available in Capacity Forecast is volume capacity, where this feature tells us how many days left of capacity each of the volumes monitored in SolarWinds has before reaching 100% space used.

The Problem

Personally, I always loved this feature, however, there is one significant issue that could potentially mislead us in terms of real capacity remaining. The main problem I found is related to how this feature calculates the trend, as it uses a very linear approach. This means that, if at any point in time, there is a single big change on the space used of the volume (for example, a big file has been copied to the disk, or a big file has been deleted), this will impact heavily on the trend, impacting the benefit of the forecast.

When analysing trends, it is always a better practice to remove the outliers in order to have a more accurate average value. This is something that ISPs do quite often when calculating how much they have to charge their customers. They don’t report on the peak use of their bandwidth, but the 95^th percentile, which essentially means they are deliberating ignoring the top 5% of data samples. This approach, therefore, smooths out the peaks and troughs to give better insight into the more common data values.

For example on the screenshot below, there is displayed the forecast capacity of a volume where SolarWinds is telling us that the trend is going down, but actually, the trend is going up, there has been just a big drop of disk usage that is misleading the trend.

Another example would be the following screenshot, where the disk space used is kept consistent during all the period, except a single big raise of the space used, that is misleading SolarWinds as it shows the trend going up when actually is steady. Now when it comes to disk space it is by nature very difficult to predict the future, as it is not known fully if and when non-linear growth will occur, which is why different analysis viewpoints such as this are so useful.

The Solution

In order to have a more accurate value for the average growth of the disks monitored in SolarWinds, I recommend doing something similar, by ignoring the top and bottom 5% of the values, allowing us to get a much more accurate growth value.

But, how can we get this newly calculated value? All the data we need is already in the SolarWinds database, we just need to create a report that analyses the data the way we want, i.e. using a custom SQL query within the report definition.

The Report

The following report I have created shows you the top 100 volumes monitored in SolarWinds that is type ‘Fixed Disk’ and how many days are left before it reaches 100% capacity. The average growth rate is monitored ignoring a defined top and bottom percentage of all the results. By default we use 5%, however, this value can be easily modified to ignore other values such as 2%, 10% or others. We can also change the number of volumes displayed, by default is top 100, but this can be changed too.