Splunk provides some nice summary information on each data model that is not immediately apparent from the interface. From the data model management screen that lists the available data models, you will notice a small information (i) column on the far left-hand side with a greater than sign (>) next to each model.
Click on this sign, and information pertaining to the data model and acceleration summaries will be displayed, including the build status of the acceleration summary and the space on disk that the summary is using, as shown in the following screenshot. You can also force a rebuild or update of the acceleration summary: