STORAGE SYSTEM AND CONTROL METHOD THEREOF, IMPLEMENTING DATA REALLOCATION IN CASE OF LOAD BIAS

摘要

A storage controller allocates a real storage area to a virtual volume in chunk units each comprising a plurality of pages. In a case where load bias occurs between RAID groups, data reallocation is carried out. A real storage area inside a pool is allocated to a virtual volume 5 in accordance with a write access. A RAID group 6 comprises a plurality of chunks. Each chunk 7 comprises a plurality of pages 8. The pages 8, from within the chunk 7 that has been allocated to the virtual volume 5, are used. A data migration plan is created and stored in page units based on the load of each RAID group. When a host 2 issues a command to a migration-targeted page, data is migrated while this command is being processed.