This article applies as of PRTG 26
Monitoring Database folder
By default, historic data in monitoring database is kept for 365 days. If you want to keep less monitoring data on the hard disk, you can change the automatic data purging limits, navigate to Setup | System Administration | Core Server. Under Historic Data Purging | Historic Sensor Data, you can change how long PRTG retains historic data.
To generally save disk space, it is a good option to enable NTFS compression for the PRTG data directory. In modern Windows versions, this does not drain performance, but saves a lot of disk space.
Alternatively, you can move the data directory from the default to a larger hard drive. For more information, see the Knowledge Base: How can I change the data directory of my PRTG installation?
Note: We strongly advise against PRTG files and database being stored on network shares. We see frequently write/read locks and other performance issues that happen on installations whose configuration files and databases are on a network location. Due to the type of I/O PRTG produces, there is a huge amount of individual read/write operations that can affect performance on network shares, so we strongly recommend to keep these files locally on the server.
