FortiConnect is used to connect Fortinet devices.
Article Id 196630
This article describes how to ‘clean up’ unused disk space from Forticonnect.

Related Links.

Data Retention page#103
Managing backup: page#425
Radius Authentication logs: page#490

1) Disabling and deleting radius logs.

Radius authentication setting has to be disabled (unchecked) on FortiConnect else it fills the memory using authentication logs:

Radius debug does not have to run in debug mode.
If it is, then go to Radius Client and select 'Restart Radius Service'.
This will move radius debug to normal mode.

2) Data retention.
2.1) Setting the data retention.
- Go  to Server -> Data Retention -> Settings and Select 'Enable'.
- Select required Policy :
• Delete Only
• Archieve to FTP and delete 'Moves the files to mapped FTP server and then delete the file'.
• Archieve to SFTP and delete 'Move the files to mapped TFTP server and then delete the files'.
-Select 'Save'.

2.2) Scheduling data retention.
- After performing initial settings mentioned in before, set the frequency of data retention as 'Daily / Weekly / Monthly' and select 'save'.

- With data retention enabled and required policy with frequency is set the older data will get deleted accordingly.
If policy is not set then data retention has to be performed manually.

2.3) Maually perform data retention.
- To manually delete the files, enable data retention and select 'Process Now'. This will temporarily override (but will not change the already schedule parameter) current settings and will process data retention.
- Specify to process Unused accounts by specifying number of days in 'Expire Inactive for : xxx days' and select 'Process Unused Accounts'.

Step-2 of 2.3 are effective while performing manual data retention but as a best practice both steps has to be performed one after the other.

3) Delete old Backup files.
- Navigate to Server -> backup/Restore -> Manage Backup Files.
- Download and delete old backups from list.