Method and system for mirroring and archiving mass storage

A computer program product for implementing, in a primary system that has a primary mass storage and is in communication with a secondary system that has a secondary mass storage, a method for mirroring and archiving the primary mass storage on the secondary mass storage, the computer program product comprising:

• a computer-readable medium carrying computer-executable instructions for implementing the method, the computer-executable instructions, when executed, causing the primary system to:
• synchronize the secondary mass storage with the primary mass storage;
• track changes to the primary mass storage during a time interval;
• identify an end of the time interval by identifying when the primary mass storage is in a logically consistent state;
• consolidate the tracked changes by retaining any tracked changes necessary to represent the state of the primary mass storage at the end of the time interval, so as to create an update that includes the retained changes but does not include tracked changes that represent an intermediate state of the primary mass storage;
• and
• transfer the update to the secondary mass storage, the update including only the changes that are required for bringing the secondary mass storage device current with the logically consistent state of the primary mass storage device.

A computer program product for implementing, in a primary system that has a primary mass storage and is in communication with a secondary system having a secondary mass storage, a method for mirroring and archiving the primary mass storage by transmitting to the secondary mass storage only those changes to the primary mass storage that are necessary to bring the secondary mass storage current with the primary mass storage while representing a plurality of logically consistent states of the primary mass storage, the computer program product comprising:

• a computer-readable medium carrying computer-executable instructions that, when executed, cause the primary system to perform:
• initiating synchronization of the secondary mass storage with the primary mass storage;
• and
• for each of a plurality of distinct time intervals:
• changing data stored in storage locations of the primary mass storage;
• identifying when the primary mass storage is in a logically consistent state, so as to identify an end of a current time interval of the plurality of distinct time intervals;
• as the data is changed, storing information representing all changes that have been made in the storage locations during the each of the plurality of time intervals in updates that correspond to the plurality of time intervals;
• consolidating the stored information in each update by retaining, for each storage location that has changed during the corresponding time interval, the information representing the most recent change to the particular storage location for that update, with the information representing any previous changes to the particular storage location being discarded for that update, such that each update includes only the changes that are required for bringing the secondary mass storage device current with the primary mass storage device as the data in the primary mass storage device exists at the end of the corresponding time interval;
• and
• transferring each update to the secondary mass storage at the end of the corresponding time interval, wherein each update is stored at the secondary mass storage such that the plurality of logically consistent states of the primary mass storage are determinable from the plurality of updates stored at the secondary mass storage.