Abstract: A case for receiving removable hard disks is disclosed. The case comprises a hard disk array circuit board, a plurality of sliding grooves provided on either side, a plurality of cartridges each disposed between two opposed sliding grooves, a plurality of sliding rails provided on either side being in cooperation with the sliding grooves such that a cartridge may slide between two opposed sliding rails, and a pivotal member provided in the front of the cartridge for inserting a SCSI disk into the cartridge, the cartridge capable of being inserted into the case by sliding the cartridge along the sliding groove, the cartridge and the case being secured together by clinging the pivotal member to the case. Hard disks of the invention are connected in a hard disk array configuration such that it is possible to remove a SCSI disk in a turn-on state of computer system and serially connect more SCSI disks than the prior art.