I am experiencing a third failure of a drive in 18 months. I have a “My Book World”. The last recovery I had to purchase a 2nd unit and move the good drive into it and let it re-sync. I think I may need to do that again. I don’t need the “World” part of the NAS so I can just buy a regular “My Book,” 1T mirrored? Will the drive from a “My Book World” be read by any model of “My Book”? Can I use different model hard drives as A and B?