The size of the CAS database depends mostly on the number of days the data is stored (default:10 days), but there is no precise formula. The largest known CAS databases are 400-500 GB. Databases of this size can cause performance problems. A good practice is to keep the database size below 200-300 GB.
It is difficult to estimate the size of the CAS database because it does not depend on the amount of traffic monitored by the AMDs that feed the CAS, or on the number of sessions in the CAS database. Databases with a relatively low number of sessions may be large if all sessions are active all the time. Databases with a large number of sessions may not be very large if each session is active for only short periods.
For the ADS estimated capacity, check the following link: