Patent ID: 6718447
Filing Date: 2004-04-06
Classification: G06F

Abstract:
A method for backing up a primary logical unit within a data storage device, the primary logical unit and a backup logical unit together comprising a mirror-logical-unit pair, the backup logical unit an active member of a pool of backup logical units managed by a controller of the data storage device, the method comprising:receiving a trigger I/O request by the data storage device; inserting a TRIGGER message corresponding to the I/O request into a queue that contains a portion of a sequenced stream of I/O requests directed to the primary logical unit; dequeing the TRIGGER message from the queue, and initiating a mirror split operation directed to the primary logical unit; sending the TRIGGER message to the backup logical unit; upon receiving the TRIGGER message by a controller handling the backup logical unit, deactivating the active backup logical unit, activating a least recently active backup logical unit within the pool of backup logical units, synchronizing the activated backup logical unit with the primary logical unit; and receiving and executing mirror I/O requests on the activated backup logical unit; and after completion of the mirror split operation, maintaining the backup logical unit as a backup copy of the primary logical unit.