Disk drive enclosure optimized for mixed slim and half high drive sizes

A disk drive enclosure houses a mix of "slim" and "half high" disk drive sizes in almost any order. The preferred enclosure includes at least thirteen equi-spaced pairs of guide rails, wherein each pair of rails includes one rail on one side panel of the enclosure, and the other rail of the other side panel of the enclosure. Each pair of guide rails defines a boundary of a "slot", such that twelve slots are defined between thirteen pairs of guide rails. Groups of slots are defined, wherein each group includes six contiguous slots. For each group of six slots, four connectors are included on a back panel of the enclosure. Within each group of six slots, the four connectors are positioned within the first, third, fourth and fifth slots, and no connectors are positioned in the second and sixth slots. A "no go" tab is also placed, adjacent the leading edge of one of the side panels of the enclosure, in the second and sixth slots to prevent the insertion of the rails of a disk drive in these slots. A removable back panel "shuttle" is included, which can be replaced with a different shuttle to easily and inexpensively convert the enclosure to receive a different type of disk drive.