Am not really 'tackling' it ... not a programmer ... more like 'dealing with it' and have found what works for the school districts I support. It does involve the timing of the site cron and some non-interactive bash shell scripts running the command line version of course backup in a cron of it's own.
But ... take a gander here:
https://moodle.org/mod/forum/discuss.php?d=319114
Think Mr. Bragg has found something that could also apply to your site since both of you guys are running 2.9.x (all of the schools I support are at either 2.7.highest or 2.8.highest).
'spirit of sharing', Ken