Order the servers from lowest to highest usable capacity.

A.
2RU (6 x 1 TB), 2RU (12 x 1 TB), 2RU (6 x 2 TB), 2RU (12 x 2 TB)

B.
2RU (6 x 1 TB), 2RU (6 x 2 TB), 2RU (12 x 1 TB), 2RU (12 x 2 TB)

C.
2RU (12 x 2 TB), 2RU (12 x 1 TB), 2RU (6 x 2 TB), 2RU (6 x 1 TB)

D.
2RU (12 x 2 TB), 2RU (6 x 2 TB), 2RU (12 x 1 TB), 2RU (6 x 1 TB)