by Ken Task.
Ok ... here's some 2 cent thoughts ... none of which gives you a real answer ... just adds to the planning.
1. one doesn't need to backup moodledata in it's entirety ... many of the directories like sessions wouldn't be needed on a restore - same is true of cache and localcache. The most important is filedir thus a minimal type backup would be filedir of moodledata only.
2. the rsync pieces would involve 2 rsync scripts .. one for the daily increments and one for the total (minimal).
3. the tiiming of all those ... don't think you'd want all sites to kick in their rsync cron jobs at the same time nor their minimal.
4. then there is DB dump as well. filedir (minimal) and db dump should match.
5. other considerattions ... are we doing automated backups of courses? On large sites with large courses auto backups takes time away from the other types of backups one might like to do.
Know that one shouldn't rely on the virtual OS backups alone ... good to have pieces/parts to moodle backed up ... I prefer to have those on the same server for easy/quick restore if at all possible.
And I think that some sites will take longer than others ... depending upon site.
More considerations ... using repos like Google Drive or Dropbox? Those are controlled else where ... only thing you have might be url's.
Some sites do some things outside of Moodle (might be in a directory mixed in with Moodle code rather than in moodledata - videos/audios[podcast]).
Sooooooo ???? Don't think I've ever done the same thing with sites ... much depends on factors that are unique to the sites - IMHO.
'spirit of sharing', Ken