The topic of adding RAID-style parity to DrivePool was raised several times on the old forum. I've posted this FAQ because (1) this is a new forum and (2) a new user asked about adding folder-level parity, which - to mangle a phrase - is the same fish but a different kettle.   Since folks have varying levels of familiarity with parity I'm going to divide this post into three sections: (1) how parity works and the difference between parity and duplication, (2) the difference between drive-level a