[insidious]

Sup' Zeus
I'm not pro at server backend stuff, i've dabbled here and there but i'll give a shot at helping you out

What/where are you backing up to? I'd say backup in two places in the least, so that you have a double-failsafe kind of thing

also, i'd probably 'tar (s3cmd sync etc etc) 'everything for the compression -- will probably save up some space. depends what you have on the server though, if it's not that much stuff it probably doesn't matter. But if you store videos/pictures and stuff tar will save you lots of space

i looked up s3cmd and it's the amazon web service command for backup and stuff, and i'm assuming 'sync' syncs you're already downloaded/backed up files.

Overall, however, if you're happy with the script and it backs up what it's supposed to in a safe way, i'd say it's OK.
If it were me, i'd probably add functions to split stuff into weeks. IE: the week of 5/13/2016 is this backup, 5/20/2016 this backup etc. Just for convenience. When I did backups of my websites, I found it helpful to go back and look at last weeks config or something like that.