The C: drive is running out of space. Investigation finds several gigabytes of .bin files found in C:\ProgramData\AppRecovery\IndexEntriesMaps
When mounting a recovery point the index files will be created in the IndexEntriesMaps folder. Every mounted partition will have a .bin file created. These files are 1MB per 1GB of the total partition size.
In some scenarios these files are not correctly removed and may accumulate over time.
This includes but not limited to Stopping the Rapid Recovery Core service while recovery points are mounted. This includes Virtual Standby, Exchange and SQL checks jobs.
Make sure to stop the Rapid Recovery Core service gracefully.
Windows Registry Disclaimer:
Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 “Description of the Microsoft Windows registry” at Microsoft Support.
Windows registry for advanced users - Windows Server | Microsoft Docs
Restarting the Rapid Recovery Core service will attempt to clear out any data in C:\ProgramData\AppRecovery\IndexEntriesMaps
If the files still are not cleared out, the .bin files are safe to delete manually.
The IndexEntriesMaps can be pointed towards a different volume if the C: drive has insufficient space.
This can be modified the from the MountMapPath registry key,