AppFormix Plan helps the user to understand, plan, and model the capacity of their infrastructure.


Allocated Capacity

In OpenStack, the unit of compute resource allocation is an instance of a particular flavor. A flavor defines the amount of vcpus, memory, and local storage allocations for an instance.

In the Plan panel of the Dashboard, a pie chart indicates the current number of allocated instances on a per-flavor basis. This provides an operator with an understanding of the types of resources requested by users of the infrastructure.

To understand the change in capacity over time, line charts show the history of allocated and available capacity in terms of the number of instances of each flavor type. Using the drop down menu, a user can choose to see the used, available or peak capacities of the infrastructure. Each line on the chart represents one flavor type. The time period displayed by the charts is configurable to view trends over long or short time horizons, and plan for appropriate resource capacity.

Allocated capacity is also displayed on a per-resource basis. The allocated percentage of capacity is displayed for for compute, memory, and storage resources.

Available Capacity

The available capacity table shows the number of instances of each flavor type that can be allocated presently. The available capacity takes into consideration the resource requirements of each flavor type, the current unused capacity of the physical infrastructure, and scheduler policy that constrains which sets of hosts can be used to allocate an instance of a particular flavor.

Modeling Oversubscription Policy

The oversubscription policy of the OpenStack Nova scheduler affects the available capacity of the infrastructure. In "Settings" > "Oversubscription", AppFormix has a configuration for oversubscription ratios. AppFormix uses these ratios when calculating the available capacity. The ratios configured in AppFormix do not affect the configuration of the scheduler.

A user may modify the ratios to model how an oversubscription policy will affect the available capacity of the infrastructure. When the ratios are modified, the available capacity table will update to show how many instances of each flavor type may be allocated. By configuring different modeling ratios, an administrator can see the impact of potential changes to the oversubscription policy of the scheduler, or understand how increasing physical capacity in the areas of compute, memory, and storage will address the demands of users.

Upon initial installation, the oversubscription ratios in AppFormix are set to 1 (i.e., no oversubscription). When not modeling a policy change, we recommend configuring the ratios to match the configuration of the OpenStack Nova scheduler policy so the available capacity table reflects the actual capacity of the infrastructure.