Patent ID: 9665286
Date: 2017-05-30
CPC Classifications: G06F

Claim:
1. A storage device comprising: a plurality of semiconductor memory units each having a plurality of nonvolatile semiconductor memory chips and a memory controller that compresses data and stores the compressed data into the nonvolatile semiconductor memory chips; and a storage controller that controls a plurality of RAID groups including a prescribed number of semiconductor memory units contained in the semiconductor memory units, and controls data writing and reading into and out of the semiconductor memory units, wherein the memory controller is configured to associate a plurality of memory areas of the nonvolatile semiconductor memory chips with a plurality of logical memory areas and makes the logical memory areas available to the storage controller, and to provide information on a physically used quantity which is an amount of the memory areas of the nonvolatile semiconductor memory chips used for storing the data, to the storage controller, and wherein the storage controller is configured to: divide the logical memory areas made available by each of the semiconductor memory units into a plurality of entries, each of which is a logical memory area of a prescribed size, manage, for each of the semiconductor memory units, a data storage quantity which is an amount of the memory areas of the nonvolatile semiconductor memory chips storing write data, structure, for each of the RAID groups, a plurality of extents each containing one of the entries belonging to the semiconductor memory units included in each RAID group, select, on the basis of the data storage quantity, a first RAID group and a second RAID group out of the RAID groups, and exchange, on the basis of the data storage quantity, data of a first extent out of the extents belonging to the first RAID group with data of a second extent out of the extents belonging to the second RAID group.