Abstract: Data to be retrieved from a non-volatile storage medium is identified by considering previously stored cache data in a cache buffer is disclosed. When a request for data is received from a host, the requested data is ear-marked for retrieval, with a desired amount of pre-read data and a desired amount of pre-fetch or read-ahead data. It is then determined whether any of the data is already in the cache buffer, and how much of a gap, if any, exists between the desired data and that already stored in the cache buffer. If some of the data is already in cache, then a controller has to satisfy the read request with a single continuous retrieval of data from the storage medium, such that the data as stored in the cache buffer is not interrupted by gaps within the cache buffer. In this manner, buffer usage rate is increased while maintaining the same cache hit rate in a particular access pattern to evaluate hard disk drive performance.

Abstract: Methods for controlling and storing data in a cache buffer in a storage apparatus having a nonvolatile memory medium are disclosed. Memory cells are logically divided into a plurality of pages. An open status is registered in a counter for each page that has at least some (and usually all) memory cells available to store new data. A full status is registered in the counter for each page that does not have memory cells that are available to store new data. New data is stored in pages having the open status in the counter. The pages can be weighted according to the read command rate and prioritized for reading and writing purposes.

Abstract: A method and apparatus for determining the position of a head with respect to a rotating magnetic disk within a disk data storage device using standard signals output from a head/drive assembly (HDA). Servo zone detect pulses are used to determine the position of the read/write head with respect to the servo cells. An index pulse determines the angular position of the head. A servo zone counter is incremented by one in response to a servo zone detect pulse. Accordingly, the servo zone counter maintains a unique value which is corresponds to each data wedge on a surface of the disk. A servo clock has a constant number of cycles between sectors. The servo clock is coupled to the clock input of a sector counter. A sector pulse is generated and the sector counter is reset to zero when the number of cycles counted indicates that the beginning of a sector is under the read/write head. A sector ID counter counts the number of sector pulses.