Information processing apparatus

An information processing system comprising:

• a storage device;
• a write request acceptance unit for accepting a write request including
• a data;
• a hash value acquisition unit for carrying out a process to acquire a first hash value by inputting the data included in the write request to a first hash function and to acquire a second hash value by inputting the data to a second hash function, when the write request is accepted;
• and
• a storage processing unit for correlating the data included in the write request, the acquired first hash value, the acquired second hash value, and information of referenced times denoting a predetermined initial value as the number of times the data has been referenced, and newly storing the correlated items into the storage device when the storage device has not stored a first hash value identical to the acquired first hash value and a second hash value identical to the acquired second hash value in correlation with each other, whereas changing the information of referenced times stored in correlation with the first hash value and the second hash value such as to add one to the number of times denoted by the information of referenced times when the storage device has stored a first hash value identical to the acquired first hash value and a second hash value identical to the acquired second hash value in correlation with each other.