1.2. Timeline and Strong Data Consistency

HBase guarantees timeline consistency for all data served from Region Servers in secondary mode, meaning all HBase clients see the same data in the same order, but that data may be slightly stale. Only the primary Region Server is guaranteed to have the latest data. Timeline consistency simplifies the programming logic for complex HBase queries and provides lower latency than quorum-based consistency. By contrast, strong data consistency means that the latest data is always served. However, strong data consistency can greatly increase latency since only the primary region server is guarnateed to have the latest data. The HBase API allows application developers to specify which data consistency is required for a query. See Querying Replicas for more information.


The HBase API contains a new method,Result.isStale(), to indicate whether data returned in secondary mode does not contain the latest write operation to the primary region server.

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