Patent ID: 8639872

Claim:
A hybrid drive comprising: a disk comprising a plurality of data tracks, each data track comprising a plurality of data sectors; a head actuated over the disk; a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments; and control circuitry operable to: define a disk cache comprising a plurality of the data sectors and a NVSM cache comprising a plurality of the memory segments; receive a write command from a host including write data; determine whether to write the write data to one of the disk cache and the NVSM cache in response to a disk counter and a NVSM counter; write the write data to one of the disk cache and the NVSM cache; increment the disk counter when data is written to the disk cache; increment the NVSM counter when data is written to the NVSM cache; and flush the write data to a non-cache area of the disk.