Modular dense storage arrays are disclosed. In some embodiments, a modular storage array may include a chassis configured to receive a plurality of drive bay modules, a first of the plurality of drive bay modules configured to receive a first plurality of storage drives in the absence of a drive adaptor, each of the first plurality of storage drives having a first form factor, and a second of the plurality of drive bay modules configured to receive a second plurality of storage drives in the absence of the drive adaptor, each of the second plurality of storage drives having a second form factor different from the first form factor.