I recently got asked to investigate an issue for a friend where their R1Soft backups stopped working and so they had to reboot their webserver.

Rebooting webservers unnecessarily in a shared environment is not a great idea, the machine loses cache, as does the database, so as well as the outage you face 15 minutes or so whilst the server performs very poorly by comparison.

What I found was that r1soft was getting confused by the cagefs mounts.

# cagefsctl --reinit

This can be done with very little outtage, most PHP apps continuing to run on the native PHP version without issue.