A magnetic disk storage system in which magnetic disk drives can be cooled effectively, and even if a blast device for one of he magnetic disk drives fall into trouble or cease operation, a temperature rise of this magnetic disk drive can be suppressed to the minimum. For this purpose, in the magnetic disk storage system containing a plurality of magnetic disk drives, blase devices ae provided for each of the disk drives, and the disk drives are separated by partitions in which openings are formed so that the cooling air can be passed between adjacent magnetic disk drives. With this structure, even if a blast device for a certain magnetic disk drive is out of order or stopped, a part of the cooling air from a blase device for the adjacent disk drives flows into the magnetic disk drive in question through the openings formed in the partitions, and consequently, the temperature rise of the magnetic disk drive whose blase device ceases operation can be suppressed to the minimum, to thereby enhance the reliability of the magnetic disk storage system.