I apologize if this isn't the right subreddit for this...
First, RAID is NOT A BACKUP STRATEGY. I have a separate backup strategy. The goal here is redunancy for the sake up uptime in case of drive failure.
In terms of redundancy, I'm not clear what advantage RAID 5 has over RAID 1 (mirroring). I understand the advantage is supposed to be that you get more useable storage out of a set of drives (3/4 of the total drive capacity).
However, for instance, these days four 5 TB drives costs over $700 (a RAID 5 setup), whereas two 16TB drives (RAID 1) costs just over $400. On each, total capacty of 15-16TB. RAID 1 is faster.
Why would anyone want to go with RAID5? Would it just be the need for a total capacity larger than 32TB, which is the maximum drive size right now?