Patent ID: 7055059

Claim:
A system for remote mirroring of data, said system comprising: a first data storage system, and a second data storage system remote from the first data storage system and linked to the first data storage system for transfer of data between the first data storage system and the second data storage system; wherein the system for remote mirroring of data is programmed to configure logical units of storage in selected mirroring configuration states such that each logical unit of storage is either local to either the first or second data storage system, or is a member of a remotely mirrored pair including a primary logical unit of storage in one of the first or second data storage systems and a secondary logical unit of storage in the other of the first or second data storage systems; and wherein the system for remote mirroring of data is programmed to maintain each remotely minored pair in a selected synchronization mode including a synchronous mode and at least one asynchronous mode, and for said at least one asynchronous mode, the data storage system containing the primary logical unit of storage of said each remotely mirrored pair is programmed to maintain a record of changes pending to the secondary logical unit of storage of the remotely mirrored pair in order to facilitate synchronization of the secondary logical unit of storage of said each remotely mirrored pair with the primary logical unit of storage of said each remotely minored pair.