by Ken Task.
I understand what you are saying, but still contend that a box where user inserts a number might be more problematic than perceived. Don't think moodle can calculate in advance what number of backups would max out the space for the size of backups themselves can't be determined yet. Courses may not exist, yet. The where to save setting could be set to 'course backup filearea' which translates to moodledata/filedir/ or it could be a specified directory ... which could be mount point to a XTB drive attached, or it could be set to both.
Heck, it's dangerous enough, IMHO, with the 100's values for some sites.
Case in point ... Moodle for a high school ... one course backup is 90+ Gig!!!! Site cannot run automated backups for that one course is too large ... and growing ... autobackups won't complete all courses ... hits the 90+Gigger and fails ... schedule for the remainder gets messed up .. the next run should pick up on the courses that are remaining to be backed up but doesn't. Now just imagine if the Moodle Admin set autobackups to keep all.
'spirit of sharing', Ken