System for selectively storing stripes of data in tracks of disks so

Abstract

A method and apparatus for bandwidth balancing of data transfer operations between a computer and a storage subsystem are disclosed. The storage subsystem contains a number of storage devices such as magnetic disk drives. Data to be stored is supplied by the computer to the storage subsystem in the form of a transfer unit through a communication channel. The storage subsystem divides the transfer unit into a number of stripes of a pre-determined size. Each stripe is allocated to a separate disk drive whose disk surfaces are formatted into a number of track bands. Each track band is composed of several contiguous tracks associated with the same data transfer rate. Each stripe is then stored on its disk drive within a selected track band. Both data storage and retrieval from each disk drive occur at the data transfer rate associated with the accessed track band. Since all the stripes in the transfer unit are transferred to their disk drives simultaneously, the transfer operation occurs at an aggregate transfer rate equal to the sum of the individual track band transfer rates. The storage subsystem selects the track bands on each disk drive in such a manner as to ensure that the data transfer operation occurs at an aggregate transfer rate within a pre-determined bandwidth range of the communication channel bandwidth.