Good backups are essential. My brother uses a similar service called Carbonite and he swears by it.

Yes, no matter what you want to keep, back it up.

I'm never sure so I back up all of our home directories. We mainly use Xubuntu Linux so that's all of our personal data. I back up in house to two backup servers. I rsync everything to one server with 11 TB. I am working on my second server using a backup program called Restic. I recommend this approach only if you are a retired computer consultant who builds machines for fun and is always looking for something to do with them. I'm literally surrounded by computers. To my right is the Hairy Larry Rocks server running Yunohost. https://hairylarry.rocks To my left is my HP workstation where I do most of my work and my MixRemix server running a LAMP stack. http://mixremix.cc And in front of me is my proxy server directing web traffic for my server subnet and an extra big UPS to keep things running when the lights go out. If you don't really understand everything I'm talking about here you might want to use an online backup service like Follow Me And Die does. (I'm not just a gaming geek, I'm a computer geek too.) Cheers!

SO has set up something that backs up my personal stuff onto a network thing every hour and that thing itself backs up the critical stuff to Baidu Cloud daily.

He did this the day after he had to spend three weeks painstakingly recovering a decade of pictures from a hard disk that broke... :-/

Yep, the only thing harder than making good backups is not making backups. It's not if you lose your data it's when. I don't know how many times I've preached this. When I would take on a new client the first thing I made them do was put a backup system in place. And then I would check it. I wouldn't do anything until then because I have been known to make mistakes too. The last thing I wanted to happen was them telling people that their new computer guy lost their data.