Patent attributes
In one implementation, a storage system comprises host computers, a management terminal and a storage system having block interface to communicate with the host computers/clients. The storage system also incorporates a deduplication capability using chunks (divided storage area). The storage system maintains a threshold (upper limit) with respect to the degree of deduplication (i.e. number of virtual data for one real data) specified by users or the management software. The storage system counts the number of links for each chunk and does not perform deduplication when the number of reduced data for a chunk exceeds the threshold, even if duplication is detected. In another implementation, the storage system additionally incorporates a data migration capability and migrates physical data to high reliability area such as area protected with double parity (i.e. RAID6) when the deduplication level for a chunk exceeds the threshold.
