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US 8,275,951 B2Granted
Local bitmaps for an array of redundant storage devices
AssigneeHewlett-Packard Development Company, L.P.
InventorsJohn J. Andruszkiewicz, Robert A. Brooks, Andrew C. Goldstein, Leonard S. Szubowicz, James J. Friedrichs
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Abstract
In accordance with at least some embodiments of the invention, a system comprises a plurality of computers coupled together and to an array of redundant storage devices that is accessible to the plurality of computers. Each of the plurality of computers comprises a local memory that stores at least one bitmap. The least one bitmap logs regions of the redundant array that have been modified.
Claims21
A system, comprising:
- a plurality of computers coupled together, each computer comprising a local volatile memory;
- an array of redundant storage devices accessible to the plurality of computers;
- and
- at least one bitmap set that includes a master bitmap and at least one local bitmap;
- wherein the at least one local bitmap is stored in the local volatile memory of one of the plurality of computers to log modifications made to the array only by the particular computer of the plurality of computers where the local bitmap is stored;
- wherein the master bitmap logs modifications made by each of the plurality of computers to the array of redundant storage devices, said modifications logged in the master bitmap identifying regions of storage in the storage devices that have been modified;
- and
- wherein at least one of the computers stores a bitmap policy that specifies a plurality of bitmap sets and, for each bitmap set, identifies one or more computers that is to host a master bitmap.
5 more elements
A method, comprising:
- in a bitmap policy, defining a reset event that causes a bitmap set to be reset;
- wherein the bitmap set relates to an array of storage devices accessible to a plurality of computers;
- and
- clearing at least one bit of the bitmap set in response to the reset event, thereby indicating that a region represented by the cleared bit is not to be included in a subsequent merge;
- wherein the bitmap set comprises a master bitmap that identifies regions of storage in an array that have been modified by the plurality of computers and at least one local bitmap that logs modifications made to the array only by a particular computer of the plurality of computers in whose volatile memory the local bitmap is stored;
- and
- wherein the bitmap policy identifies one or more of the computers to host the master bitmap set.
4 more elements
A method, comprising:
- when a master bitmap is present among a bitmap set hosted by a plurality of hosts:
- selecting the host of the master bitmap from the plurality of hosts based on the presence of the master bitmap;
- associating the master bitmap with an array of redundant storage devices by examining a bitmap policy that specifies a plurality of bitmap sets and, for each bitmap set, identifies one or more hosts that is to host a master bitmap associated with each such bitmap set;
- and
- performing a bitmap based merge of the contents of the storage devices identified in the master bitmap to maintain consistency of data in the storage devices;
- and
- when a master bitmap is not present and a local bitmap is not present, performing a full merge of the contents of the storage devices.
4 more elements
A system, comprising:
- means for creating a bitmap set comprising a master bitmap that identifies regions of an array of redundant storage devices that have been modified by a computer cluster and at least one local bitmap that logs regions of the array that have been modified only by the one computer in the computer cluster where the local bitmap is stored, said means for creating creates the bitmap set based on a bitmap policy that specifies a plurality of bitmap sets and, for each bitmap set, identifies one or more computers in the computer cluster that is to host the master bitmap associated with each such bitmap set;
- means for storing the master bitmap;
- means for storing the at least one local bitmap in local volatile memory of one computer in the computer cluster;
- means for performing a bitmap based merge of the contents of the storage devices at a location determined from the master bitmap when the master bitmap is present;
- and
- means for performing a full merge of the contents of the storage devices when no master bitmap is present and no local bitmap is present.
3 more elements
Dependencies are inferred from the claim text.