How to reproduce:
1. Set a thinBackup schedule.
2. Create a periodic (or SCM-triggered) job which runs for a long time.
3. Create other jobs which run quickly.
1. The slow job starts.
2. thinBackup triggers, and sets Jenkins to "quiet down" mode, not allowing any more jobs to start.
3. Any triggered or scheduled fast jobs now have to wait for the slow job and the backup to finish before continuing.
4. While thinBackup is waiting for the jobs to finish, "Jenkins is going to shut down" is prominently shown on every page.
As this waiting time could be very long, this can mean a large amount of time wasted because of idling machines and waiting developers. The warning message is also misleading enough to make this a major issue.
To be able to run frequent backups without losing time, it would be nice if thinBackup could simply not set Jenkins to "quiet down" mode, and instead back up only builds which are finished. If this is done in a similar fashion to rsync (copying only files which are newer than the target) there shouldn't even be any problems with jobs modifying older builds (for example as part of post-build tasks).
Workaround: Set the schedule to back up only when people aren't using Jenkins.