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US 7,743,216 B2Granted
Predicting accesses to non-requested data
AssigneeSeagate Technology LLC
InventorsClark E. Lubbers, Michael D. Walker
Life of this patent
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AssigneeSeagate Technology LLC
InventorsClark E. Lubbers, Michael D. Walker
Estimating the term…
Method and apparatus for caching and retaining non-requested speculative data from a storage array in an effort to accommodate future requests for such data. A cache manager stores requested readback data from the storage array to a cache memory, and selectively transfers speculative non-requested readback data to the cache memory in relation to a time parameter and a locality parameter associated with a data structure of which the requested readback data forms a part. The locality parameter preferably comprises a stream count as an incremented count of consecutive read requests for a contiguous data range of the storage array, and the time parameter preferably indicates a time range over which said read requests have been issued. The speculative readback data are transferred when both said parameters fall within a selected threshold range. The data structure preferably comprises a RAID stripe on a selected storage device of the array.
An apparatus comprising a cache manager configured to adaptively initiate a transfer of speculative non-requested data from a data structure portion of a storage array responsive to a stream count of read requests for consecutive data from said portion greater than a predetermined stream count threshold and a measured elapsed time interval since a most recent access of said portion of the storage array less than a predetermined time interval threshold.
A method comprising steps of storing requested readback data from a data structure portion of a storage array to cache memory, and transferring speculative non-requested readback data from said portion to the cache memory in conjunction therewith in relation to an elapsed time parameter associated with said portion less than an elapsed time threshold and a locality parameter associated with said portion greater than a stream count threshold.
An apparatus comprising a controller having associated programming in a computer memory, the programmed controller adapted to direct a transfer of requested data from a portion of a storage array to a cache memory responsive to read requests from a host device, to accumulate a plural count of said read requests for data from said portion, to measure an elapsed time interval associated with said count, and to direct a transfer of speculative non-requested data from the portion to the cache memory in conjunction with the requested data when the accumulated count and the measured time interval respectively satisfy predetermined threshold values that define a sequence of speculative non-requested data transfer decision points.
Dependencies are inferred from the claim text.