Adaptive file readahead technique for multiple read streams

The storage system which carries out the storage operating system constituted so that conjectural prediction might be simultaneously carried out to several different read-out streams. Unlike the conventional enforcement form, this operating system holds a prediction metadata set individual about each of two or more read-out streams. Therefore, this operating system coincides the received client read request with a corresponding read-out stream, and can carry out prediction processing to that demand according to the prediction metadata set relevant to a read request. Since it is in agreement with a read-out stream corresponding for every demand, the received client read request an operating system, It cannot be concerned with whether the file reading request in a read-out stream is received in order by the storage system, it is received mostly in order, or it is received at random, but prediction processing can be simultaneously carried out to two or more read-out streams. Furthermore, even if it is a case where the prediction algorithm from which a read-out stream differs is being used, the operating system can carry out conjectural prediction simultaneously to several different read-out streams. The present invention can be carried out also with those combination also by the storage system of a block base with the storage system of a file base.