US Patent 7890691 Memory cache sharing in hybrid hard disk

A system allows one or more hybrid hard disks or any other storage devices to share a logical nonvolatile device formed by one or more non-volatile memory devices. The system comprises a control logic to reserve on a hybrid hard disk a space that corresponds to a non-volatile memory device in the hybrid hard disk and to use a space access instruction to access the non-volatile memory device. The control logic accesses the logical non-volatile memory device in an event that a content of a storage device is stored in the logical non-volatile memory device in response to an instruction to access the storage device.