All concerts and CDs are stored in a 4 drive SATA Array, each SATA is a 2tb WD Green Cavier Drive--very quiet very low heat. The drives are RAIDed with RAID 0 (Striping)
Those are backed up once a week to an identical 4 drive SATA Array with FOLDER CLONE via RAID Controller Card and cord, probably an eSATA.
Those are backed up once a month to a single 2tb SATA drive via USB
Those are backed up every other month to another single 2tb SATA drive via USB
Back Ups are performed by FOLDER CLONE, a $30 product which scans the source and target and compares them, and then only writes over what needs to be changed, e.g., deleting and copying only those files/folders to make the target an exact clone. Back Ups take only a few minutes, if not much is changed. Brilliant program, easy to use, very intuitive, and cheap. It stores data in same format, e.g., flac or mp3, not in a compressed format.