RAID is complicated, and getting it right is difficult. You don’t want to wait until your drives are failing to learn about a gap in your understanding of RAID. For this reason, I recommend ZFS to most. It automatically makes good decisions for you with respect to mirroring and parity, and gracefully handles rebuilds, sudden power loss, and other failures. It also has features which are helpful for other failure modes, like snapshots. Set up Zed to email you reports from ZFS. Zed has a debug mode, which will send you emails even for working disks — I recommend leaving this on, so that their conspicuous absence might alert you to a problem with the monitoring mechanism. Set up a cronjob to do monthly scrubs and review the Zed reports when they arrive. ZFS snapshots are cheap - set up a cronjob to take one every 5 minutes, perhaps with zfs-auto-snapshot.

these days hardware RAID is almost always a mistake. Most operating systems have software RAID implementations which can achieve the same results without a dedicated RAID card.

RAID gets more creative with three or more hard drives, utilizing parity, which allows it to reconstruct the contents of failed hard drives from still-online drives.