There was a problem writing in-memory hints to disk.
When writing hints to the hints_directory location defined in the cassandra.yaml, some disk or filesystem issue has occurred that prevents the hint from being written.
- Verify the hints_directory is accessible and Cassandra has permissions on the directory (see example below).
drwxr-xr-x 2 cassandra cassandra 4096 Sep 21 18:49 hints
- Check operating system logs (e.g. /var/log/messages) for disk device issues.