Patent ID: 7185222

Claim:
An apparatus for maintaining data in an electronic storage array during multiple drive failures, the apparatus comprising: a primary response module configured to recognize a failure of a first drive of a plurality of storage drives forming volume set accessible to a storage controller and to enter a first operating mode in response to the failure of the first drive, the first operating mode comprising placing the first drive in an off line state and placing the volume set in a modified read/write mode using non-failed drives of the volume set; and a secondary response module configured to recognize a failure of a second drive of the volume set and to enter a second operating mode in response to the failure of the second drive, the second operating mode comprising placing the drives of the volume set in a read-only mode with the failed second drive in a degraded state wherein the storage controller attempts to read requested data from the failed second drive and from a pinned data drive in response to the requested data being unavailable from the failed second drive.