Patent ID: 7013317

Claim:
A method for managing backup of data stored in first and second storage devices structuring a mirrored pair, said method comprising: at a first time, (a) managing whether updating is carried out or not to each of data blocks of said first and second storage devices using first and second update-management tables; said data blocks being respectively partitioned in said first and second storage devices; and said first and second update-management tables corresponding respectively to said first and second devices and respectively indicating any update to each of said data blocks of said respective first and second storage devices, (b) stopping a process of carrying out updating to said second storage device, and (c) starting an updating process of said second update-management table to hold the same information as said first update-management table; at a second time which is after said first time or at the same time as said first time, (d) stopping said updating process of said second update-management table, (e) resetting said first update-management table to a state in which no update has been carried out to the data blocks of said first storage device, and (f) copying, to a backup medium, data of said second storage device stored in at least one of said data blocks indicated by said second update-management table as being updated; and at a third time which is after said second time, (g) copying data of said first storage device stored in at least one of said data blocks indicated by said second update-management table as being updated to at least one of data blocks of said second storage device corresponding to said data blocks of said first storage device, and (h) then making contents of said second update-management table coincide with contents of said first update-management table.