Method of controlling data writing to persistent storage device

A computer system comprising:

• a first computer;
• and
• a plurality of second computers, wherein
• the first computer includes:
• a persistent storage device that stores a set of data, identification information of the data, and a version number of the data;
• and
• a first controller,
• each of the second computers includes:
• a cache that holds copy data of the data acquired from the persistent storage device;
• and
• a second controller,
• the second controller of the second computer transmits, to the first computer, confirmation data including the identification information and the version number of the copy data updated in the cache of an own computer,
• based on the confirmation data received from the second computer and information stored in the persistent storage device, the first controller of the first computer extracts the identification information and the version number corresponding to the copy data to be written to the persistent storage device, from the confirmation data received from the second computer, and transmits response data including the extracted identification information and the extracted version number to the second computer, and
• based on the response data received from the first computer and information stored in the cache, the second controller of the second computer determines the copy data stored in the cache to be transmitted to the first computer so as to be written to the persistent storage device.

A storage computer connected with a plurality of cache computers, each having a cache, over a network, the storage computer comprising:

• a persistent storage device that stores a set of data, identification information of the data, and a version number of the data;
• and
• a controller, wherein
• from the cache computer holding, in the cache, copy data of the data stored in the persistent storage device, the controller receives confirmation data including the identification information and the version number of the copy data updated in the cache,
• based on the received confirmation data and information stored in the persistent storage device, extracts the identification information and the version number corresponding to the copy data to be written to the persistent storage device, from the confirmation data received from the cache computer, and
• transmits response data including the extracted identification information and the extracted version number to the cache computer.

A cache computer connected with a storage computer over a network, the storage computer including a persistent storage device that stores a set of data, identification information of the data, and a version number of the data, the cache computer comprising:

• a cache that holds copy data of the data acquired from the persistent storage device;
• and
• a controller, wherein
• the controller configured to update the cache by copy data, transmit, to the storage computer, confirmation data including the identification information and the version number of the copy data updated in the cache,
• receive, from the storage computer, response data including the identification information and the version number corresponding to the copy data to be written to the persistent storage device,
• based on the response data received from the storage computer and information stored in the cache, determine the copy data in the cache to be transmitted to the storage computer for writing to the persistent storage device, and
• transmit the determined copy data to the storage computer.

A non-transitory computer readable medium storing a program comprising instructions for causing a storage computer to function as, the storage computer being connected with a plurality of cache computers, each having a cache, over a network:

• a persistent storage device that stores a set of data, identification information of the data, and a version number of the data;
• and
• a controller, wherein
• from the cache computer holding, in the cache, copy data of the data stored in the persistent storage device, the controller receives confirmation data including the identification information and the version number of the copy data updated in the cache,
• based on the received confirmation data and information stored in the persistent storage device, extracts the identification information and the version number corresponding to the copy data to be written to the persistent storage device, from the confirmation data received from the cache computer, and
• transmits response data including the extracted identification information and the extracted version number to the cache computer.

A non-transitory computer readable medium storing a program comprising instructions for causing a cache computer, connected with a storage computer, to function as, the storage computer including a persistent storage device that stores a set of data, identification information of the data, and a version number of the data:

• a cache that holds copy data of the data acquired from the persistent storage device;
• and
• a controller, wherein
• the controller transmits, to the storage computer, confirmation data including the identification information and the version number of the copy data updated in the cache,
• receives, from the storage computer, response data including the identification information and the version number corresponding to the copy data to be written to the persistent storage device, and
• based on the response data received from the first computer and information stored in the cache, determines the copy data in the cache to be transmitted to the storage computer so as to be written to the persistent storage device.