Abstract: A worker node included in a storage system 1 includes a score calculation unit 31 that calculates a score of the worker node based on a failure history and an operation status of the worker node, and a master node (P) includes a promotion node selection unit 52 that compares scores for each worker node when a failure occurs in one of master nodes and selects, based on the scores, a worker node to be promoted to a master node instead of the master node in which the failure has occurred.

Abstract: A worker node included in a storage system 1 includes a score calculation unit 31 that calculates a score of the worker node based on a failure history and an operation status of the worker node, and a master node (P) includes a promotion node selection unit 52 that compares scores for each worker node when a failure occurs in one of master nodes and selects, based on the scores, a worker node to be promoted to a master node instead of the master node in which the failure has occurred.

Abstract: A computer system includes a cluster. The cluster includes nodes, which are allowed to hold communication to and from one another over a network, and which are configured to store user data from at least one calculation node. The nodes include old master nodes. The nodes each includes reference information, which indicates master nodes of the cluster. The computer system is configured to add, when a failure occurs in a master node that is one of the old master nodes, new master nodes to the cluster in a number equal to or larger than a minimum unit number of master nodes, which is determined in advance in order to manage the cluster. Each old master node that is in operation out of the old master nodes is configured to rewrite the reference information held in each old master node so that the new master nodes are indicated.

Abstract: A first node transmitting a non-extension read command which is a read command for reading out data without extending, and in which command a logical address is designated that corresponds to compressed data, to a first nonvolatile memory device. The first node transmits a transfer command to a second node via a network. The transfer command is for transferring between nodes the data to be transferred, the transferred object being the compressed data read out without extending by the first nonvolatile memory device in response to the non-extended read command. The second node transmits, in response to the transfer command, a write command for which the compressed data is the target to write to a second nonvolatile memory device.

Abstract: A first node transmitting a non-extension read command which is a read command for reading out data without extending, and in which command a logical address is designated that corresponds to compressed data, to a first nonvolatile memory device. The first node transmits a transfer command to a second node via a network. The transfer command is for transferring between nodes the data to be transferred, the transferred object being the compressed data read out without extending by the first nonvolatile memory device in response to the non-extended read command. The second node transmits, in response to the transfer command, a write command for which the compressed data is the target to write to a second nonvolatile memory device.