Patent ID: 8635400

Claim:
A storage system comprising: a plurality of first storage devices and a plurity of second storage devices, each of the plurality of first storage devices including a plurity of flash chips, each having a plurality of physical blocks as a unit of data deletion, and a first device controller balancing data deletion among the physical blocks within the first storage devices; each of the plurality of second storage devices including a second device controller; and a storage controller configured to: configure a plurality of first RAID groups, each of which has a set of first storage devices in the plurality of first storage devices and includes a plurality of first data areas, each of the plurality of first data areas being divided into each of the set of first storage devices in the first RAID group; and configure a plurality of second RAID groups, each of which has a set of second storage devices in the plurality of second storage devices and includes a plurality of second data areas, each of the plurality of second data areas, being divided into each of the set of second storage devices in the second RAID group, and each of the plurality of first and second data areas being for storing at least one record set including a plurality of data records and the parity record generated from the plurality of data records, wherein the storage controller is configured to: obtain a first information relating to data deletion of each of the plurality of first storage devices; select at least one first RAID group of the plurality of first RAID groups from which a record set is transferred based on the first information of first storage devices and at least one second RAID group of the plurality of second RAID groups to which the record set is transferred; and transfer the record set in one of the plurality of data areas from the first RAID group to the second RAID group.