Please follow the below steps to reduce the Disc space storage in NetFlow Analyzer:
1. Stop NetFlow Analyzer service.
2. Open command prompt as administrator and navigate to NetFlow_Home/troubleshooting
3. Execute rawCleanup.bat and wait until the process completes.
4. Exclude complete NetFlow_Home directory from any antivirus scan or automatic backup application running in the server.
5. Tune NetFlow Analyzer as mentioned in the below link:
For Mysql :
https://forums.manageengine.com/topic/nfa-professional-edition-performance-tuning-tips
For Postgres:
https://forums.manageengine.com/topic/manageengine-netflow-analyzer-performance-tuning-steps
6. Start the NetFlow Analyzer service and navigate to Admin--> Storage Settings --> Raw Data Settings and select Retain Raw Data to the lowest time period and check on the issue.