The Image Builder Service appears as Healthy with warnings in the vCenter Server Appliance Management Interface (VAMI).
The warning message displayed is: "Running out of available space."
Upon inspection, the Image Builder directory has ample free space available.
VMware vCenter Server
Image Builder calculates the cache size rather than the total directory size.
Increase the Image Builder cache size to twice its current configured value.
To do this, navigate to: Auto Deploy > Configure > "Edit" under VMware Image Builder Service.