In a disk control system having a RAID controller for continuously writing data on a data stripe composed of a plurality disk apparatus, in response to a write request, data blocks are sequentially written on empty areas of a write target data stripe on the plurality of disks in such a manner that at least one data block is written at a time. Further, in response to the write request, logical addresses having address values prior to address translation are written on logical address log areas on the plurality of disks, as logical-address log information. An upper file system is notified that the write has been completed after the data and the logical-address log information have been completely written.