Raid is not a backup, but I use Linux md raid on my file server for all mass data storage so don't have to worry about drive failures or at very least not a single one. Beauty is not having to lose any productivity, no need to copy data anywhere or restore anything. Just pop another drive in and I'm good to go. (or wait, does not matter, but I like to do it asap)
For actual backups I have various rsync jobs that copy data to one of the raid arrays that is dedicated for backups, I also have a drive dock that I do a backup to when I remember... and now that I think of it, it's been a while. I have several drives I rotate around with different jobs assigned to them. Typically I bring the large one to work which covers my most critical stuff. That is like my total last resort backup if the house burns down type deal. I also have some offsite rsync backup jobs that run weekly to my web server. I need to also look at cloud, but I'd want something that supports rsync so I don't need to come up with a different way to automate it. Actually I need to look at rdiff backup too. Overall I do need a massage storage upgrade so I can have better backups. Most of my backups are simply a mirror, with some oddball stuff dated monthly/weekly/daily such as databases.
Oh and to those curious this is my file server setup:
The middle one is where all the data is, the top one is a VM server (only has an OS drive) and the bottom stuff I don't really use but it's some SAN enclosures that are hooked up to the file server via fibre channel. Was awesome at the time, but for the power it uses and fact that I can't put my own drives in it, I find it's practically useless, so I will take them out if I need the rack space.
Right now the file server has 3 raid arrays:
Filesystem Size Used Avail Use% Mounted on
/dev/md0 5.4T 3.5T 1.7T 69% /volumes/raid1
/dev/md1 6.3T 5.4T 571G 91% /volumes/raid2
/dev/md3 7.2T 1.8T 5.1T 26% /volumes/raid3
Not that much disk space by today's standards but I can expand as I need. md1 is a bunch of 1TB drives, I am due to upgrade that array to much larger drives. In fact all my arrays use rather small drives as that's what was economical to get at the time. md0 and md3 are raid 10, md1 is raid 5. That is my oldest array, it's dated 2008. It's been transplanted between like 3 different machines lol. That's the beauty of software raid though, you're not depending on specific hardware.