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Mechanism for determining read-ahead length in a storage system

  • US 8,732,406 B1
  • Filed: 03/15/2011
  • Issued: 05/20/2014
  • Est. Priority Date: 03/15/2011
  • Status: Active Grant
First Claim
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1. A method for managing an amount of read-ahead data, comprising:

  • monitoring client read operations, a client read operation requesting data blocks representing a read stream;

    populating a data structure with read stream sizes and read stream counts based upon the client read operations;

    evaluating the data structure to select a first read stream having a first read stream size;

    evaluating the data structure to identify a set of read streams, where read streams within the set of read streams have read stream sizes equal to or greater than the first read stream size;

    generating a stream metric corresponding to the read stream sizes and a count of the read streams within the set of read streams;

    determining an expected size of a target read stream based upon the stream metric, the determining comprising;

    determining a probability that the first read stream corresponds to the expected size; and

    adjusting the expected size, comprising;

    responsive to the probability exceeding a first threshold, decreasing the expected size; and

    responsive to the probability exceeding a second threshold, increasing the expected size; and

    reading ahead a number of data blocks corresponding to a difference between the first read stream size and the expected size after the adjusting.

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