Putting Plex’s main metadata directory on a USB drive, mounted in /media by the automounter, is asking for trouble
Experience has shown that moving PMS’s metadata on a persistent partition , such as /home is the best. Other internal HD’s, mounted with ‘exec’ option, are also viable.
Fundamental requirements are:
Local file systems only - Network shares are not safe due to file locking requirements
A linux-native file system formatting - xfs, btrfs, or ext4
3, drive / partition mounted in /etc/fstab with exec privilege asserted.
Changing where PMS’ metadata is (moving from /var/lib/plexmediaesrver)