초록 ▼

The disclosure relates to sequential performance of a cached data storage subsystem with a minimal control signal processing. Sequential access is first detected by monitoring and examining the quantity of data accessed per unit of data storage (track) across a set of contiguously addressable tracks

The disclosure relates to sequential performance of a cached data storage subsystem with a minimal control signal processing. Sequential access is first detected by monitoring and examining the quantity of data accessed per unit of data storage (track) across a set of contiguously addressable tracks. Since the occupancy of the data in the cache is usually time limited, this examination provides an indication of the rate of sequential processing for a data set, i.e., a data set is being processed usually in contiguously addressable data storage units of a data storage system. Based upon the examination of a group of the tracks in a cache, the amount of data to be promoted to the cache from a backing store in anticipation of future host processor references is optimized. A promotion factor is calculated by combining the access extents monitored in the individual data storage areas and is expressed in a number of tracks units to be promoted. The examination of the group of tracks units and the implementation of the data promotion and demotion (early cast-out) is synchronized which results in a synergistic effect for increasing throughput of the cache for sequentially-processed data. A limit of promotion is determined to create a window of sequential data processing.

대표청구항 ▼

In a method of operating a cache which is interposed between a host processor and a backing store, the cache and the backing store including addressable like-capacity data storing tracks, where a track of data is the amount of data storable on one track of a magnetic disk recorder the cache includin

In a method of operating a cache which is interposed between a host processor and a backing store, the cache and the backing store including addressable like-capacity data storing tracks, where a track of data is the amount of data storable on one track of a magnetic disk recorder the cache including means for addressing tracks in the cache using addresses of the backing store whenever the cache tracks are individually allocated for storing data with respect to a respective addressable track in the backing store; the steps of: measuring and storing the measurement of those portions of each of said allocated tracks that are accessed by the host processor during the current allocation of the cache track to one of the tracks in the backing store; selecting a group of the cache tracks that are addressable by contiguous ones of the backing store addresses; establishing first and second access extent thresholds; in each of the selected groups, comparing, as at first comparison, the stored measurement for one of the tracks in the selected group with said first access extent threshold, if the first comparison shows that the stored measurement for the one track is less than the first access extent threshold, operating the cache for said one cache track in a random access mode, if the first comparison shows that the one cache track stored measurement is greater than the first access extent threshold, then combining the stored measurements for all cache tracks in the group having the one cache track; and comparing, as a second comparison, said combined stored measurement with said second access extent threshold, if said second comparison shows that the combined measurement exceeds said second access extent threshold, preparing the cache for cache bypass operations, if said second comparison shows that the combined measurement is not greater than said second access extent threshold, then establishing for tracks in the backing store having addresses contiguous with the backing store address of the one cache track a predetermined requested data promotion and demotion algorithm.