I've been using actual raid5 (via adaptec raid card) for years and very recently had one of my trusty 5TB HGST drives fail (after 3+ yrs of uptime).
Fortunately the rebuild worked, but there are so many horror stories of raid5 rebuilds NOT working it has me contemplating going back to simple mirroring.
If you are going to use hardware raid, please do make sure you have a spare raid controller, same firmware, same model. If not, you will be SOL when your controller dies.
RAID5 these days (with our very large disks) is basically asking for trouble - the odds of a second disk failing during the reconstruction are very high. But I guess you already know that!
Now I use a more sophisticated RAID10 setup and really appreciate the way failed and replaced drives automatically rebuild themselves without my dumb interaction.
I would also mention it's probably a good idea to use something like ZFS rather than a hardware RAID card. In general, free software RAID is better audited and you don't need specific hardware for the recovery process. But also, ZFS has proper checksumming, so you won't have to worry about all sorts of silent corruption (which RAID blissfully ignores -- most implementations will just recompute the parity in case of a mismatch, which is the wrong thing to do (1-1/n) of the time).
Was hoping to utilize ZFS in 20.04... but the whole SNAP issue has me sticking with my current version.
Perhaps it's time to find a dummies guide to setting up ZFS on 18.04 LTS.
As an IT Exec (retired)... this was a lesson learned long ago. For my own/home systems I use rclone [i] (in conj w raid5) for the most critical files.