Method and system for providing consistent data modification information to clients in a storage system
First Claim
1. A storage system for providing data consistency to multiple clients, comprising:
- a facility for storing data and data modification information, wherein the data is stored as data blocks; and
a request processor for handling requests for data from the clients, said request processor capable of identifying data that has been modified during a given time interval based on the modification information and updating the modification information to ensure that the data accessed by the clients will be consistent, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Toggle Block Map includes a plurality of bits, each bit corresponding to a data block and said bit complemented when the data block is modified.
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Abstract
A data storage system and method for providing consistent data to multiple clients based on data modification information as existing data is updated and new data is written to the system. The information indicates the modification status of each data block and identifies which data blocks have been modified during a certain time interval. The clients may query and update the modification information by submitting requests through a request processor. The data modification information includes an Altered Block Map that indicates block modification status and a Toggle Block Map that identifies which blocks have been modified. The system further includes a Modification Counter a Pending Reset Counter for improved recognition and handling of the modified data.
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Citations
27 Claims
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1. A storage system for providing data consistency to multiple clients, comprising:
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a facility for storing data and data modification information, wherein the data is stored as data blocks; and
a request processor for handling requests for data from the clients, said request processor capable of identifying data that has been modified during a given time interval based on the modification information and updating the modification information to ensure that the data accessed by the clients will be consistent, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Toggle Block Map includes a plurality of bits, each bit corresponding to a data block and said bit complemented when the data block is modified. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a storage system including a facility for storing data and data modification information and a request processor for handling requests for data from clients, a method for providing data consistency comprising the steps of:
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identifying data that has been modified during a given time interval based on the modification information, wherein the data is stored as data blocks, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Toggle Block Map includes a plurality of bits, each bit corresponding to a data block and said bit complemented when the data block is modified;
accessing the modified data; and
updating the modification information to ensure that data accessed by the clients will be consistent. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A computer-program product for use with a storage system including a facility for storing data and data modification information and a request processor for handling requests for data from clients, the computer-program product comprising:
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a computer-readable medium;
means, provided on the computer-readable medium, for identifying data that has been modified during a given time interval based on the modification information, wherein the data is stored as data blocks, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Toggle Block Map includes a plurality of bits, each bit corresponding to a data block and said bit complemented when the data block is modified;
means, provided on the computer-readable medium, accessing the modified data; and
means, provided on the computer-readable medium, for updating the modification information to ensure that data accessed by the clients will be consistent. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A storage system for providing data consistency to multiple clients, comprising:
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a facility for storing data and data modification information, wherein the data is stored as data blocks; and
a request processor for handling requests for data from the clients, said request processor capable of identifying data that has been modified during a given time interval based on the modification information and updating the modification information to ensure that the data accessed by the clients will be consistent, wherein the data modification information includes an Altered Block Map, and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Altered Block Map includes a plurality of bits, each pair of bits in the Altered Block Map corresponding to a data block and including a Modification Bit and a Pending Reset Bit, the Modification Bit is set whenever the data block is modified by a write request, and the Pending Reset Bit is set whenever the data block is requested by a client.
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26. In a storage system including a facility for storing data and data modification information and a request processor for handling requests for data from clients, a method for providing data consistency comprising the steps of:
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identifying data that has been modified during a given time interval based on the modification information, wherein the data is stored as data blocks, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Altered Block Map includes a plurality of bits, each pair of bits in the Altered Block Map corresponding to a data block and including a Modification Bit and a Pending Reset Bit, wherein the Modification Bit is set whenever the data block is modified by a WRITE request and the Pending Reset Bit is set whenever the data block is requested by a client;
accessing the modified data; and
updating the modification information to ensure that data accessed by the clients will be consistent.
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27. A computer-program product for use with a storage system including a facility for storing data and data modification information and a request processor for handling requests for data from clients, the computer-program product comprising:
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a computer-readable medium;
means, provided on the computer-readable medium, for identifying data that has been modified during a given time interval based on the modification information, wherein the data is stored as data blocks, wherein the data modification information includes an Altered Block Map and a Toggle Block Map, the Altered Block Map indicating the modification status of the data blocks and the Toggle Block Map indicating which data blocks have been modified, wherein the Altered block Map includes a plurality of bits, each pair of bits in the Altered Block Map corresponding to a data block and including a Modification Bit and a Pending Reset Bit, wherein means are provided on the computer-readable medium, for setting the Modification Bit whenever the data block is modified by a WRITE request, and means are provided on the computer-readable medium, for setting the Pending Reset Bit whenever the data block is requested by a client;
means, provided on the computer-readable medium, accessing the modified data; and
means, provided on the computer-readable medium, for updating the modification information to ensure that data accessed by the clients will be consistent.
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Specification