Journal migration method and data recovery management method

A computer system, comprising:

• a first storage subsystem;
• a first server coupled to the first storage subsystem;
• a second storage subsystem;
• and
• a second server coupled to the second storage subsystem and, via a network, to the first server,
• wherein the first storage subsystem has a first storage unit, which stores data requested by a host computer to be written, and a first control unit, which controls input/output of data to/from the first storage unit,
• wherein the second storage subsystem has a second storage unit, which stores data requested by the host computer to be written, and a second control unit, which controls input/output of data to/from the second storage unit, and
• wherein the first server is configured to:
• record journals related to data stored in the first storage unit;
• identify, in the case where one of a part and all of pieces of data stored in the first storage unit is to be migrated to the second storage unit, which ones of the recorded journals are related to the data that is to be migrated;
• choose the identified journals one at a time in reverse chronological order;
• judge whether or not the chosen journal corresponds to a data update made at some point between a current time and a time that precedes the current time by a length of a journal retention term set for the second server;
• send, upon judging that the chosen journal corresponds to the update, the chosen journal to the second server via the network;
• and
• stop, upon judging that the chosen journal does not correspond to the update, choosing the journals.

A first storage subsystem coupled to a second storage subsystem via a network, comprising:

• a first storage unit which stores data requested by a host computer to be written;
• and
• a first control unit which controls input/output of data to/from the first storage unit,
• wherein the first control unit is configured to:
• record journals related to data stored in the first storage unit;
• identify, in the case where one of a part and all of pieces of data stored in the first storage unit is to be migrated to the second storage subsystem, which ones of the recorded journals are related to the data that is to be migrated;
• choose the identified journals one at a time in reverse chronological order;
• judge whether or not the chosen journal corresponds to a data update made at some point between a current time and a time that precedes the current time by a length of a journal retention term set for the second storage subsystem;
• send, upon judging that the chosen journal corresponds to the update, the chosen journal to the second storage subsystem via the network;
• and
• stop, upon judging that the chosen journal does not correspond to the update, choosing the journals.