| 摘要 |
Various embodiments of the present invention provide methods, in distributed data-storage systems that associate one or more timestamps with each data block in each data-storage-component, for deciding whether or not a data block has been written. In certain embodiments of the present invention, a sparse database of timestamps associated with data blocks is maintained, each timestamp having a field that contains one of an indication of a time or sequence and a sentinel value indicating that the timestamp is garbage collected. When a timestamp is not found associated with a data block in a timestamp database, the data block is associated with a garbage-collected-timestamp state. In various embodiments of the present invention, data structures are maintained that store status information indicating whether or not any of a number of data blocks in each of a number of data-block-allocation units have been written. During replication, migration, or reconfiguration of a current segment of data blocks to a new segment of data blocks in these various embodiments, a data block is determined to be written or to be unwritten by determining, from the data structures, whether or not a data block-allocation unit containing the data block is written or unwritten.
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