Storage system and storage control method

A storage system comprising,

• a nonvolatile storage device;
• a processor configured to operate as a storage controller for processing read and write from and to the storage device;
• and
• a memory,
• wherein the storage device has a permanent area in which data is destaged and permanently stored and a cache data log area in which a cache data log is stored to make the cache data log non-volatile, the memory has a cache data area,
• the processor is configured to:
• when receiving a write request, store data related to the write request in the cache data area provided in the memory,
• create a log header having a sequence number related to memory storage of the data, store the log header and the data stored in the memory in the cache data log area of the storage device, respond to a request source of the write request, and register the sequence number of the created log header in an invalidation table,
• destage the data stored in the memory to the permanent area of the storage device, create a log header having a sequence number related to the destage, and register the sequence number in the invalidation table,
• when the cache data log area of the storage device is collected by a garbage collection method, delete a log header having a sequence number older than the sequence number registered in the invalidation table and data related to the log header from the cache data log area to release the storage area
• when the cache data log area of the storage device is collected by the garbage collection method, specify the corresponding partial area based on the address information of the log header that is the determination target of collection necessity,
• compare the sequence number associated with the specified partial area in the invalidation table with the sequence number of the log header, and determine, if the sequence number of the log header is a number earlier than the sequence number stored in the invalidation table, a log indicated by the log header to be unnecessary and perform collection, and
• determine, if the sequence number of the log header is not a number earlier than the sequence number stored in the invalidation table, the log indicated by the log header to be necessary, create the log in a new area of the cache data log area, and perform the collection.

A storage control and garbage collection method for controlling a storage system, the storage system including a nonvolatile storage device, a processor configured to operate as a storage controller for processing read and write from and to the storage device, and a memory, the storage device having a permanent area in which data is destaged and permanently stored and a cache data log area in which a cache data log is stored to make the cache data log non-volatile, the memory having a cache data area, the storage control and garbage collection method comprising:

• by the processor,
• when receiving a write request, storing data related to the write request in the cache data area provided in the memory;
• destaging the data stored in the memory to the permanent area of the storage device;
• collecting the cache data log area of the storage device;
• when storing the data in the cache data area provided in the memory, creating a log header having a sequence number indicating a log order related to memory storage of the data, storing the log header and the data stored in the memory in the cache data log area of the storage device, responding to a request source of the write request, and registering the log header in a cache data log header management list provided in the memory corresponding to the cache data log area;
• upon the first destaging step, destaging the data stored in the memory to the permanent area of the storage device, creating a log header having a sequence number of a log related to the first destaging step, and registering the sequence number in an area corresponding to an address of the memory where the destaged data has been stored, in an invalidation table;
• when collecting the cache data log area of the storage device, comparing the sequence number of the log header registered in the invalidation table with the sequence number of the log header stored in the cache data log header management list in the memory with respect to each target address;
• and
• deleting a log header having a sequence number older than the sequence number of the log header registered in the invalidation table and data related to the log header from the cache data log area to release the storage area.