Disk array apparatus and method for dividing and reading/writing partial data across a plurality of drive groups utilizing parallel processing

Claim 1

A disk access method in a disk apparatus, wherein a disk controller is connected to a plurality of drives each having a plurality of memory disks, said method comprising the steps of: grouping a plurality of said drives into a plurality of drive groups; dividing a data set into a plurality of partial data each having a data quantity processible at one time by each of said drive groups when an access request is generated from an external apparatus to said disk apparatus so as to write said plurality of partial data of said data set into said drives; writing a plurality of said partial data into a plurality of said drive groups in a dispersed manner, wherein at least two partial data are written into different drive groups at different times, and successive partial data are written into different drive groups; and reading out a plurality of said partial data forming a designated data set among the data sets stored in a dispersed manner in a plurality of drive groups when an access request for reading out said designated data set is generated from said external apparatus to said disk apparatus, wherein said writing step and said reading step are executed by parallel processing in a plurality of said drive groups by sequentially issuing access requests to said plurality of said drive groups and starting processing to a present access request before completion of processing of a previous access request.