The invention discloses a data storage system and a managing method thereof. The data storage system according to the invention accesses or rebuilds data based on a plurality of primary logical storage devices and at least one spare logical storage device. The primary logical storage devices are planned into a plurality of data blocks in a first RAID architecture. The at least one spare logical storage device is planned into a plurality of spare blocks in a second RAID architecture. The data storage system according to the invention utilizes a plurality of virtual storage devices and several one-to-one and onto functions to distributedly map the data blocks and the spare blocks to a plurality of blocks in a plurality of physical storage devices.