# US 11,307,789 B2 · Storage system and storage control method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,307,789 B2 - Document ID: US11307789B2 - Status: Granted - Kind: B2 - Application number: 17/008,733 - Filed: 2020-09-01 - Published: 2020-12-17 - Granted: 2022-04-19 - Earliest claimed: 2018-09-21 - Assignees: Hitachi, Ltd. - Applicants: Hitachi, Ltd. - Inventors: Kenta Sato; Akira Deguchi; Tomohiro Kawaguchi - Web page: https://patentgrep.com/patent/US11307789B2 ## CPC - G06F 3/0647: {Migration mechanisms} - G06F 3/0604: {Improving or facilitating administration, e.g. storage management} - G06F 3/0626: {Reducing size or complexity of storage systems} - G06F 3/0634: {by changing the state or mode of one or more devices} - G06F 3/0658: {Controller construction arrangements} - G06F 3/067: {Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]} - G06F 11/203: {using migration} - G06F 11/2071: {using a plurality of controllers} - G06F 11/2092: {Techniques of failing over between control units} - H04L 67/1095: Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes - H04L 67/1097: for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS] - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A storage system and storage control method are provided in which a plurality of volumes to be processed by a storage control unit are distributed and evacuated in a normal storage control unit without recovering redundancy of the storage control unit having decreased redundancy, and the storage control unit itself having the decreased redundancy is deleted after the evacuating is completed, and thus reservation information processing resources for guaranteeing recoverability of the redundancy become unnecessary. ## Claims ### Claim 1 A storage system comprising a plurality of storage nodes constituting a cluster, a storage apparatus storing data, a cluster control unit controlling the storage system, and a storage control unit, in a storage node of the plurality of storage nodes, providing a storage area in units of volume to a host apparatus by using the storage apparatus and storing data in the storage apparatus in response to an input/output (I/O) request from the host apparatus, the storage control unit in the storage node is configured to constitute a first storage control unit group with a storage control unit of another storage node in the cluster, wherein a storage control unit of the first storage control unit group processes the I/O request from the host apparatus as a storage control unit in an active mode and another storage control unit of the first storage control unit group takes over processes of the storage control unit in the active mode, and wherein the cluster control unit obtains information about a volume handled by the first storage control unit group, determines a second storage control unit group with respect to the volume about which the information is obtained, and migrates the volume handled by the first storage control unit group from a storage control unit within the first storage control unit group to a storage control unit of the second storage control unit group. ### Claim 2 (depends on 1) The storage system according to claim 1, wherein the storage system is configured to delete the first storage control unit group, after the volume has been migrated. ### Claim 3 (depends on 2) The storage system according to claim 2, wherein a migration of the volume is performed when a number of operating nodes decreases due to a reduction or a failure. ### Claim 4 (depends on 3) The storage system according to claim 3, wherein the migration of the volume is performed when a storage node including the volume is to be removed, the storage system is configured to migrate the volume of the first storage control unit group in which the active mode storage control unit is placed on the storage node to be removed to the second storage control unit group. ### Claim 5 (depends on 4) The storage system according to claim 4, wherein the storage system is configured to, migrate the volume of the first storage control unit group to another node, activate a standby mode storage control unit-of the first storage control unit group, when a standby mode storage control unit which is able to take over a processing of an active mode storage control unit in the first storage control unit group is placed on the node to be removed. ### Claim 6 (depends on 3) The storage system according to claim 3, wherein the migration of volume is performed when the storage node to be removed is to be removed because of a failure, the first storage control unit group in which the active mode storage control unit is placed on the node to be removed, switches storage control units located on other nodes to the active mode. ### Claim 7 (depends on 6) The storage system according to claim 6, wherein the first storage control unit group is placed on the node to be removed, includes the volume, a storage control unit group is configured by copying the volume to a node where a storage control unit of the deleted first storage control unit group is placed and no failure has occurred, and the storage control unit of the deleted first storage control unit group is activated. ### Claim 8 In a storage system having a plurality of storage nodes constituting a cluster, a storage apparatus storing data, a cluster control unit controlling the storage system, and a storage control unit, in a storage node of the plurality of storage nodes, providing a storage area in units of volume to a host apparatus by using the storage apparatus and storing data in the storage apparatus in response to an input/output (I/O) request from the host apparatus, wherein the first storage control unit in the storage node is configured to constitute a storage control unit group with a storage control unit of another storage node in the cluster, a method comprising the steps of: processing, by a storage control unit of the first storage control unit group, the I/O request from the host apparatus as a storage control unit in an active mode; taking over processing, by another first storage control unit of the storage control unit group, of the storage control unit in the active mode, and obtaining, by the cluster control unit, information about a volume handled by the first storage control unit group, determining a second storage control unit group with respect to the volume about which the information is obtained, and migrating the volume handled by the first storage control unit group from a storage control unit within the first storage control unit group to a storage control unit of the second storage control unit group. ### Claim 9 (depends on 8) The method according to claim 8, further comprising the step of: deleting the first storage control unit group, after the volume has been migrated. ### Claim 10 (depends on 9) The method according to claim 9, further comprising the step of: performing migration of the volume when a number of operating nodes decreases due to a reduction or a failure. ### Claim 11 (depends on 10) The method according to claim 10, further comprising the steps of: performing migration of the volume when a storage node including the volume is to be removed, migrating the volume of the first storage control unit group in which the active mode storage control unit is placed on the storage node to be removed to the second storage control unit group. ### Claim 12 (depends on 10) The method according to claim 10, further comprising the steps of: migrating the volume of the first storage control unit group to another node; and activating a standby mode storage control unit of the standby mode of the first storage control unit group, when a standby mode storage control unit which is able to take over a processing of an active mode storage control unit in the first storage control unit group is placed on the node to be removed. ### Claim 13 (depends on 10) The method according to claim 10, further comprising the steps of: performing migration of volume when the storage node to be removed is to be removed because of a failure; and switching, by the first storage control unit group in which the active storage control unit is placed on the node to be removed, storage control units located on other nodes to the active mode. ### Claim 14 (depends on 13) The method according to claim 13, wherein the first storage control unit group is placed on the node to be removed, includes the volume, a storage control unit group is configured by copying the volume to a node where a storage control unit of the deleted first storage control unit group is placed and no failure has occurred, and the storage control unit of the deleted first storage control unit group is activated.