Abstract: A transfer data block is selected, and a data file including the transfer data block is selected as a transfer data file. All the data blocks of the transfer data file are added to the transfer data block. When all the data files including each transfer data block is selected as a transfer data file, the transfer data block is selected as a deletion data block. When a total data amount of the deletion data block is larger than or equal to a predetermined target deletion data amount and a ratio of a total data amount of the transfer data block to the total data amount of the deletion data block is smaller than or equal to a predetermined value, the data file is transferred from a transfer source node to a transfer destination node. Accordingly, a storage can be used efficiently.

Abstract: There are provided a processing unit that processes received requests, a storage unit that stores order information added to the last-processed request among the requests processed by the processing unit as final request information, a determination unit that determines whether the received request has been processed with reference to the final request information based on the order information added to the received request, and a control unit that, when the determination unit determines that the received request has been processed, prevents the received request from being processed by the processing unit, thereby preventing overlapped execution of a command.

Abstract: An internode put requesting unit detects a time-out with respect to a put request issued to the next node in the order of a multiplexing chain and notifies a put/get executing unit of the time-out. The put/get executing unit sends an error to the previous node in the order of the multiplexing chain or a client and instructs a put-failed-data synchronizing unit to synchronize data failed to be put, and the put-failed-data synchronizing unit performs a synchronization process. A primary makes other put requests wait until completion of the synchronization process. Furthermore, when having received the error, the client issues a get request to the tail end of the multiplexing chain.

Abstract: A storage system having a plurality of storages. The each of the storages include a memory and a processor coupled to the memory. The processor executes a process including transmitting an update request for data which is commonly stored in the plurality of storages according to a predetermined transmission order indicating a path to transfer the update request. The process includes updating data when receiving an update request from another storage. The process includes changing the predetermined transmission order to a transmission order in which one or more storages included in the path are excluded according to the number of times the update request for the data is received.

Abstract: A storage device is one of a plurality of storage devices storing replicas of data. The storage device includes a memory and a processor coupled to the memory. The processor executes a process includes transmitting an update request to at least one destination storage device through a plurality of paths when the storage device is requested to update the data by a client. The process includes notifying the client that the updating of the data has been completed when having received a response through one of the paths, the response being issued by the destination storage device serving as the terminal point of the path when the destination storage device receives the update request through all the paths having the destination storage device as the terminal point.

Abstract: The disclosed method includes obtaining a result concerning a busy rate and the number of accesses per unit time for a storage device including first and second storage areas; determining, from the result, whether an event that a first indicator value for the busy rate is reset occurs; when the event occurred, notifying a controller that makes the number of accesses for the second storage area not greater than the notified number of accesses of the first number of accesses less than the second number of accesses, which was notified immediately before; obtaining another result; updating the first indicator value based on another result; calculating the third number of accesses so that a sum of busy rates corresponding to the third number of accesses and corresponding to the designated number of accesses becomes equal to the updated first indicator value; and notifying the controller of the third number of accesses.

Abstract: A data management apparatus sends specific data and key information corresponding to the specific data to another apparatus, when executing a process to change a storage destination of the specific data in which the hash value obtained by applying a predetermined hash function to corresponding key information belongs to a certain range, from the data management apparatus to the other apparatus, and sends the identification information of the other apparatus stored in correspondence with the certain range to a request source of an operation request, when the operation request with respect to data corresponding to key information is received after the process.

Abstract: A control unit shifts a boundary between a range of hash values allocated to a first node and a range of hash values allocated to a second node from a first hash value to a second hash value to thereby expand the range of hash values allocated to the first node. The control unit moves data which is part of data stored in the second node and in which hash values calculated from associated keys belong to a range between the first hash value and the second hash value, from the second node to the first node.

Abstract: Upon receipt of a first key and first data, a control unit exercises control to store second data indicating a second key in association with the first key in a first node and to store the first data in association with the second key in a second node. Upon receipt of an access request that specifies the first key, the control unit detects that data stored in association with the first key is the second data, and accesses the first data stored in the second node on the basis of the second key indicated by the second data.