However, I found that I had a lot of data to back up, and it was actually cheaper and less tedious to get 4TB USB hard drives for ~£100 each, and plug them into an old defunct EeePC901 (with the added advantage that if the power goes out it has a battery).
My main PC has an SSH private key that lets it access a restricted shell on the EeePC that only allows it to give it files to store. That way, if a hacker breaks into my internet-facing machine, all they can do to my backups is fill the disc up, not delete or access anything. I have a process on the EeePC that regularly scrubs the par2 files, and the hard drives (I have two so far) are formatted with BTRFS, so given all the data is regularly read by the scrub process, that should notice any drive failures. My main PC uses ZFS, so I have safety in variety.
I also have an off-site backup stored on an encrypted USB hard drive in my locked locker at work, which isn't updated as regularly. My internet connection is slow, so I use the rsync --only-write-batch trick, and then carry the large update file to the backup on my laptop.
What could possibly go wrong?