hbase
  • Introduction
  • Concepts
  • Hbase Architecture
    • Region servers
      • Regions
      • HFile
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      • How the Components Work Together
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      • Store(HStore OR Memstore))
      • HBase Region Flush
    • Special Tables ROOT , META
    • Fault Tolerance( Failover)
    • Data Locality
    • ZooKeeper: The Coordinator
    • HBase HMaster
    • Read Load Balancing
    • HBase Minor Compaction
    • HBase Major Compaction
    • HBase Read Merge
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    • overview-example
  • HBase Read
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  • Known Use Cases
  • HBase Data Model
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  1. Hbase Architecture
  2. Region servers

HBase Region Flush

PreviousStore(HStore OR Memstore))NextSpecial Tables ROOT , META

Last updated 5 years ago

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When the MemStore accumulates enough data, the entire sorted set is written to a new HFile in HDFS. HBase uses multiple HFiles per column family, which contain the actual cells, or KeyValue instances. These files are created over time as KeyValue edits sorted in the MemStores are flushed as files to disk.

Note that this is one reason why there is a limit to the number of column families in HBase. There is one MemStore per CF; when one is full, they all flush. It also saves the last written sequence number so the system knows what was persisted so far.

The highest sequence number is stored as a meta field in each HFile, to reflect where persisting has ended and where to continue. On region startup, the sequence number is read, and the highest is used as the sequence number for new edits.