Storage system and data protection method

A data protection method of a storage system including one or more non-volatile storage devices and a plurality of storage controllers that control reading and writing for the one or more non-volatile storage devices,

• wherein the one or more non-volatile storage devices store user data,
• wherein each of the plurality of storage controllers is coupled to a host and coupled to the one or more non-volatile storage devices and includes a processor and a memory, and each of the plurality of storage controllers are respectively physically connected to all of the one or more non-volatile storage devices in the storage system without any other storage controllers connected between the each of the plurality of storage controllers and the one or more non-volatile storage devices and each of the plurality of storage controllers is configured to control all of the one or more non-volatile storage devices without using another intervening storage controller,
• wherein each of the plurality of the storage controllers are configured to individually implement a first memory protection method that is a memory copying method, and a second memory protection method that is a log saving method, and upon a first storage controller, which is any one of the plurality of storage controllers, executing the first memory protection method, data on a first memory of the first storage controller is copied to a second memory of a corresponding second storage controller, among the plurality of storage controllers, and upon the first controller executing the second memory protection method, a log which is update content of control information related to update of the data on the first memory is generated and the log is written into a non-volatile medium,
• the data protection method comprising:
• storing, by the first storage controller, a write request from a host for the one or more non-volatile storage devices in the first memory as cache data;
• protecting, by the first storage controller, the cache data in the first memory protection method or the second memory protection method;
• returning, by the first storage controller, a write completion response to the host;
• destaging, by the first storage controller, the cache data into the one or more non-volatile storage devices after the write completion response;
• and
• switching, by the first storage controller, between the first memory protection method and the second memory protection method to be used according to an operation state of another storage controller,
• wherein in the case of the second memory protection method:
• a storage controller, among the plurality of storage controllers, recovers the state of the other storage controller after deleting the log, and
• the log is deleted without being applied after dirty data corresponding to the log is destaged to the one or more non-volatile storage devices.