Patent ID: 8635402

Claim:
A storage system having a key-value data store configuration in which a key and a value are stored in an associated manner and a key specified is searched for to find a value associated with the key specified, said storage system comprising: a storage device; and a unit means that responsive to a request to write a pair of a key and a value, calculates a hash value of said value, and stores a first pair including said key and said hash value of said value respectively as a key and a value, and a second pair including said hash value of said value and said value respectively as a key and a value, respectively in said storage device, and that responsive to a read request, searches said storage device, using a key specified by said read request, to find a hash value of a value that forms said first pair with said key specified, and searches said storage device, using said found hash value of said value, to find a value that forms said second pair with said hash value of said value, and if as a result of searching said storage device using said hash value of said value, a value that forms said second pair with said hash value of said value is not found in said storage device, determines that said first pair is not saved normally in said storage device; a volatile storage device and a nonvolatile storage device, and wherein responsive to a request to write a pair of a key and a value, said unit means saves said first pair and said second pair respectively in said volatile storage device, saves said first pair in said nonvolatile storage device at a same time said first pair is saved in said volatile storage device, or at a later time before returning a response to said write request to a requesting source, and saves said second pair in said nonvolatile storage device at a same time said second pair is saved in said volatile storage device or at any later time.