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Abstract

The disk drive array data storage subsystem maps between virtual and physical data storage devices and schedules the writing of data to these devices. The data storage subsystem functions as a conventional large form factor disk drive memory, using a plurality of redundancy groups, each containing N+M disk drives. A performance improvement is obtained by eliminating the disk formatting delays found in the prior art. In order to accommodate the need to format virtual volumes to be compatible with the form and format of the data records to be transmitted by the host processor, the present disk drive array memory system stores format information in a virtual track directory which controls the mapping of the virtual cylinders defined by the host processor into the physical elements of the disk drive array. Therefore, not only the cylinders are mapped from virtual to physical but the format of these cylinders is also mapped from the virtual format defined by the host processor to the physical configuration used by the disk drive array memory. The disk drive array memory system does not physically format the cylinders and tracks of the disk drives contained therein in response to a format command from the host processor but simply emulates this operation by writing the format data into the virtual track directory.