Patent ID: 8682874

Claim:
A method of operating an information processing system having a plurality of search nodes connected to a file server over a network, where each of the search nodes and the file server has a computer, a storage device, and a communication device, and the information processing system stores a plurality of indexes, the method comprising: searching for a file group, including one or more files, which was newly created or updated in the file server; downloading from the file server the file group which was newly created or updated; mapping the search nodes by search node IDs to a plurality of slot regions, the slot regions being formed by partitioning at regular intervals a circular hash value space in which a start point and an end point of the hash value space are identical; calculating a hash value of meta information on each file of the file group and placing the calculated hash value on the circular hash value space so as to detect one of the slot regions including the calculated hash value; determining a search node ID mapped to the detected slot region; determining one of the indexes into which each file of the file group is to be registered based on the search node ID of the search node corresponding to the respective file and creating a differential index thereof; updating the indexes stored in the information processing system using the differential index, when there are K slot regions defined for N search nodes and M search nodes are newly added, extracting KM/{N(N+M)} slot regions from each of the N existing search nodes and registering the extracted slot regions in a list in order from a top of the list for each search node; and segmenting the slot regions into segments of K/(N+M) slot regions in order from the top of the list and allocating the segments to search node IDs of the newly added M search nodes, where K, N and M are integers.