Storage system and operation method of a storage system

A storage system, comprising:

• a redundant array of independent disks (RAID) comprising a plurality of disks and a bitmap;
• a file subsystem for executing a write command to write data in blocks of the plurality of disks of the RAID, and executing a trim command to notify the RAID to release blocks of the plurality of disks of the RAID corresponding to the trim command;
• and
• a multiple device control unit for not executing a first synchronization operation on the plurality of disks during the RAID is built, not executing a second synchronization operation on expansion capacity of the plurality of disks during the RAID is expanded, executing a third synchronization operation on at least one added disk according to the blocks of the plurality of disks of the RAID occupied by the data during the RAID is reshaped, and/or executing a corresponding operation on at least one added disk according to the blocks of the plurality of disks of the RAID occupied by the data during the RAID is recovered;
• wherein the bitmap is used for recording the blocks occupied by the data.