What I don't see anything talked about is time.
If you are putting in large drives 10-18TB and have an 18TB parity drive it will take months for the parity to be created. If you lose a drive, (which I have not yet) I assume it will take just as long to rebuild the files. For things like family pictures, maybe you can wait months. For things like VM's or web application files, you need those back IMMEDIATELY. So best thing to do is create multiple backups of the files, and a cloud offiste backup too.