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Failover and failback system for a direct access storage device

  • US 6,006,342 A
  • Filed: 12/11/1997
  • Issued: 12/21/1999
  • Est. Priority Date: 12/11/1997
  • Status: Expired due to Term
First Claim
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1. A method for handling failures in a storage controller interfacing between a plurality of host systems and direct access storage devices (DASDs), comprising the steps of:

  • (a) directing data from the host systems through a first and second data paths in the storage controller to a DASD, wherein a first processor, first non-volatile memory unit (NVS), and a first cache are associated with the first data path, wherein a second processor, a second NVS, and a second cache are associated with the second data path, and wherein a bridge provides communication between the first processor and the second NVS and the second processor and the first NVS, comprising the steps of;

    (1) writing data directed toward the first data path in the first cache;

    (2) communicating with the first processor data directed toward the first data path to the second NVS via the bridge for storage in the second NVS;

    (3) writing data directed toward the second data path in the second cache;

    (4) communicating with the second processor data directed toward the second data path to the first NVS via the bridge for storage in the first NVS;

    (b) handling a point of failure within at least one of the first processor, first cache, and first NVS, comprising the steps of routing data directed toward the first data path to the second processor and writing the routed data to the second cache and the second NVS; and

    (c) rerouting data directed to the first data path to the first processor upon repairing the point of failure, wherein the rerouted data is written in the first cache and communicated with the first processor to the second NVS via the bridge for storage therein.

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