US 6,662,282 B2Granted

Unified data sets distributed over multiple I/O-device arrays

AssigneeHewlett-Packard Development Company, L.P.

InventorRobert A. Cochran

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Abstract

A hardware configuration and methodology for serializing or partially serializing WRITE requests directed to a unified data set are subsequently distributed to one or more remote arrays containing a corresponding mirror unified data set. For each unified data set, one of the local disk arrays over which the unified data set is distributed is selected as a supervisor disk array, and a unified sequence number component is included within that supervisor disk array. WRITE requests generated by a local array to mirror unified data set data to a mirror unified data set must be associated with a unified sequence number, and the WRITE requests are therefore serialized or partially serialized by the unified sequence number component. Additional direct communications links are provided between the local arrays over which a unified data set is distributed both to facilitate WRITE-request serialization and to provide a redundant communications paths for added reliability.

Claims18

Dependent claims

A data-consistent, distributed unified data set device group that stores a distributed unified data set, the distributed unified data set device group comprising:

a first data storage component, within a first supervisor local data-storage array, that stores a first portion of the distributed unified data set, the first supervisor local data-storage array receiving WRITE requests directed to the first portion of the distributed unified data set from a host computer via a communications medium, the first supervisor local data-storage array including a controller that executes a unified sequence number component that provides sequence numbers for WRITE requests directed to the data-consistent, distributed unified data set device group and that executes controller functionality for receiving, carrying out, and responding to WRITE requests received from a host computer;
a second data storage component, within a second subordinate local data-storage array, that stores a second portion of the distributed unified data, the second subordinate local data-storage array, the second subordinate local data-storage array including a controller that executes controller functionality for receiving, carrying out, and responding to WRITE requests received from a host computer;
and
a mirror unified data set that mirrors the distributed unified data set stored on one or more remote data-storage arrays.

1 more element

A method for maintaining data consistency between a unified data set distributed over two or more local data storage arrays, each containing a controller and each coupled to a communications medium, and a mirror unified data set stored on one or more remote data storage arrays, each containing a controller and coupled to a communications medium, the method comprising:

designating one of the local data storage arrays as a supervisor local data storage array, and designating the remaining local data storage arrays as subordinate local data storage arrays;
executing a unified sequence number component by the controller of the supervisor local data storage array;
prior to transmitting a mirror WRITE request directed to the mirror unified data set from a local data storage array,
requesting by the controller of the local data storage array a unified sequence number to associate with the mirror WRITE request from the unified sequence number component, and
including a unified sequence number received from the unified sequence number component within the mirror WRITE request;
under synchronous mirroring,
when the unified-sequence-number component of the supervisor local data-storage array receives a request for a unified sequence number to include in a mirror WRITE request directed to the mirror unified data set, the unified-sequence-number component of the supervisor local data-storage array
determines whether a mirror WRITE request directed to the mirror unified data set is currently pending, and
when a mirror WRITE request directed to the mirror unified data set is currently pending, queues the request for a unified sequence number to a unified sequence number request queue, and
when a mirror WRITE request directed to the mirror unified data set is not currently pending, returns a next unified sequence number to the controller of a local data-storage array;
and
under asynchronous mirroring,
when the unified-sequence-number component of the supervisor local data-storage array receives a request for a unified sequence number to include in a mirror WRITE request directed to the mirror unified data set, the unified-sequence-number component of the supervisor local data-storage array
determines whether a maximum number of mirror WRITE requests directed to the mirror unified data set are currently pending, and
when a maximum number of mirror WRITE requests directed to the mirror unified data set are currently pending, queues the request for a unified sequence number to a unified sequence number request queue, and
when a maximum number of mirror WRITE requests directed to the mirror unified data set are not currently pending, increments a count of pending mirror WRITE requests, and returns a next unified sequence number to the controller of a local data-storage array.

13 more elements

Dependencies are inferred from the claim text.