Thank you for rsnapshot plugin, it works very well. I think there is a possible easy improvement to make on it, about the way it schedules its jobs.
Today, hourly, daily, monthly and yearly cron jobs are executed with schedules set "by hand" by the dev. They are set so that two rsnapshot jobs do not collide with each other, which is not optimal. Instead of this raw duration guess, an easier and more efficient way would be use to use a lock (with the flock command) within /var/lib/openmediavault/cron.d/rsnapshot. That way, you could schedule all jobs to the same time (or nearly same time if you want to guarantee order), and flock would ensure jobs are launched immediately after the previous one.
In case you don't know the flock command, there are many tuto on the net for this.
Can it be implemented in the plugin?