Abstract: A disk-based archival storage system including a storage unit configured to store archival data, the storage unit including at least one spindle of disks configured to magnetically store archival data, an interconnect; and a control unit configured to process requests over the interconnect to either archive to or retrieve data from the storage unit. In one embodiment, the system includes a plurality of the storage units, each including at least one spindle of disks. The control unit controls the storage unit(s) in a master-slave relationship. Specifically the control unit is capable of issuing commands to selectively cause the storage unit(s) to shut down or power up, enter a running mode or a standby mode, cause the spindle of disk(s) to either spin up or spin down, and to perform a data integrity check of all the archival data stored in the storage system.