The "public" and "private" data used by the Domain and Distribution services are located in "C:\Users\Public\CA\SM" and "C:\ProgramData\CA\SM" respectively by default.
The public folder contains logs. Disk usage of this folder is generally low during normal runtime.
The private folder contains all Policies, Templates, and Deployment related files for SystemEDGE and AIM. This folder is about 1 GB in size on fresh install. This overall size of this folder will grow by a few hundred MB on upgrades (as newer sysedge deployment files are installed). It will also grow minimally during normal runtime - most files used for Policies & Templates are small (but the overall number of files will increase with each added Policy, Template and managed SystemEDGE agent).