Data transferring system having foreground and background modes and upon detecting significant pattern of access in foreground mode to change background mode control parameters

摘要

A method and apparatus for transferring data from a donor storage device to a target storage device in parallel with requests from a host computer for transfers between the host computer and the target storage device. A copy subroutine operates in response to background and foreground mode controllers. The background mode controller normally copies data from an initial position in the donor storage device sequentially by data block. When a DTR command from the host processor requests a data element from a block that has not migrated to the target storage device, the foreground controller uses the copy subroutine to transfer the designated block. The storage areas are divided into statistical blocks. If a threshold number of consecutive DTR commands accesses a particular statistical block, the system resets the parameters for the background mode controller to effectively move the copy subroutine to begin background copying from the statistical block. A subsequent request to move the subroutine in the background mode cannot occur until a minimum number of data blocks have been transferred.