Box plot charts

The box plot option allows you to view detailed information about three metrics: memory, CPU, and Disk I/O usage of both the host and its VMs. You can use the box plot option to identify trends in utilisation of VMs and hosts. When you drill-through, you are presented with box plot charts and time series. Box plot charts are also used extensively in advanced reporting across all metrics.

Basic structure of the box plot charts is as follows:

By default, metric performance data is gathered every 5 minutes for the last 3 months. This makes it possible for the day charts to be accurate to 5 minutes.

Available charts

Four charts in total are available when you open box plots from the context menu of the sunburst or from the headroom dialog window. All four are displayed when you are looking at the box plots for a host.

The charts are arranged in pairs, the chart on the left being a summary of the data presented in the chart on the right. In other words, the detailed calculations that you see in the charts on the right show how the behaviours represented here affect the item displayed in the chart on the left. For example, Host Memory demand by VM for Host chart shows data that affects the overall Host Memory demand.

Available charts are as follows:

Note

The names of the charts change depending on which metric you are viewing: CPU, memory or Disk I/O.

image

Box plot breakdown

Quartiles

Capacity Planner quartiles are bound by specific percentiles:

Note

Capacity Planner box plots do not display outliers.

Percentiles

The 100% peaks and 0% troughs are not necessarily a good indication of overall performance of the hosts. Rather than use an average, Capacity Planner uses percentile measures.

By default, the CPU measure is 95th percentile but this can be changed in the Model panel. This reflects that the value of the metric was at this level or lower 95 percent of the time that is summarised. While a sensitive measure, this is not as sensitive as the peak. Using peak can significantly overstate capacity requirements and lead to inefficient use of the resource available.

To better understand how percentiles are reflected in the box plots, see these details:

Note

Each of the percentile values is always drawn on the chart. However, two or more of the values can often be exactly the same or very near to each other. This makes it look like the one of percentiles hasn’t been drawn on the chart, when in fact it has. This often happens with the 5th & 25th percentiles and the 95th & 75th percentiles.

Peak

The peak is the 100th percentile value of usage. The peak value is used to calculate information on your Baseline View, and therefore determines how your Baseline View is coloured.

The peak is shown as a short horizontal line above the box plot.
image

Value used

A blue circle on the box plot indicates the value used in the calculations to generate your Baseline View, as summary for headroom calculations for each Host and VM. It directly affects the colouring of each segment and VM in your Baseline View.

The values are defined separately for each resource, both memory and CPU:

The value used can be changed by selecting alternative measures in the Model panel. For more information, see Statistical summaries in the Baseline View.

image

Open box plot charts

Box plot charts can be accessed from Baseline View and Forward Thinking scenario models.

To view box plot charts from a Baseline View, follow these steps:

  1. Open the Baseline View you want to see the details for.
  2. Right-click a host or VM.
  3. Click Drill-through.

The box plots are displayed, showing the CPU utilisation by default. To see box plots for other metrics, open the corresponding tab.

To view box plot charts from a Forward Thinking scenario model, follow these steps:

  1. Open the Forward Thinking scenario model you want to see the details for.
  2. Right-click a host or VM.
  3. Click Headroom. A baseline summary dialog opens.
  4. In the dialog window, click Options image next to the required metric.
  5. Click Boxplots.

The box plots are displayed, showing the metric that you selected by default. To see box plots for other metrics, open the corresponding tab.

Using box plots

When you want to see more calculations for the selected host, you need to drill through the box plots to show more data. This works the same for all available metrics: CPU, memory and disk I/O.

Change metric

To view different metrics in the box plot charts, click the tab in the top right of the window for the desired metric. Available metrics are:

View the host’s box plots and time series

To view box plots for the host, click the box plot in the host demand chart in the top left corner. The charts present the following data:

View the VM’s box plots and time series

To view box plots for a specific VM, click that VM in the Host demand by VM chart in the top right corner. All days covered by the current baseline model and summary are highlighted in the box plot charts. Time series data is not available when clicking through a summary that is not part of the current baseline model. The VM demand by date chart at the bottom updates to present the following data:

View the percentile values

Each box plot contains its percentile values. To see them, hover over the box plot to see the values.

["Capacity Planner"] ["User Guide"]

Was this topic helpful?