I agree about RAID5, but personally I don't think RAIDZ2 really works as an alternative. Everyone should use RAID10. The reason for this actually has nothing t

I agree about RAID5, but personally I don't think RAIDZ2 really works as an alternative. Everyone should use RAID10. The reason for this actually has nothing to do with data protection (although not having to read your entire disc set to rebuild is nice). The reason is that it's hard to figure out who RAID5/6 are actually for. The enterprise is all on RAID10 (hence no one fixing the BTRFS write hole). So you'd think it would be for enthusiasts who don't want to purchase as many discs, right? Well, in my case at least, parity disc modes are useless for me because it means I would have to buy discs of exactly the same size into the indefinite future! I started with 4TB discs, then I've added 8TB discs, and now I'm looking at newer Western Digital 10TB helium discs, which are actually much lower power than the 8TB ones. But none of those 4TB or 8TB discs have failed! So while in theory if stick to the drive size you start out with, you can save money with RAIDZ by using parity discs and adding a drive when you need more storage (at the cost of a decreased parity %), practically speaking a lot of that money is wasted since you either have to neglect larger more efficient drives, or replace working older drives when you want to upgrade.