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Abstract

A data storage system employs a universal timer to perform asynchronous peer-to-peer data mirroring, where primary and secondary controllers cooperatively perform periodic consistency checks according to the universal timer. The system includes multiple primary storage controllers each having a counterpart secondary controller. Primary and secondary controllers access a universal timer, such as a global positioning system (GPS). Each primary controller receives updates, and stores the updates in an order, providing each update with a sequence code according to its storage order. Each primary controller also transmits the updates and corresponding sequence codes to its secondary controller. Each secondary controller receives updates from its counterpart primary storage controller and stores the updates in a journal. Whenever a periodic timer interval of the universal timer expires, several things happen. Each primary controller sends its counterpart secondary controller a confirmation message useful in identifying all updates that were sent in the expired interval. Also, each secondary controller checks for receipt of the confirmation message, and if received, the secondary controller checks the journal for presence of all updates identified by the confirmation message. If each secondary controller finds all identified updates in its journal, all secondary controllers proceed to commit the journaled updates to secondary storage.

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First Claim