HDFS - EditLog (transaction log)

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The NameNode uses a transaction log called the EditLog to persistently record every change that occurs to file system metadata.


The NameNode to insert a record into the EditLog when

  • a new file is created
  • the replication factor of a file is changed


Offline Edits Viewer

Offline Edits Viewer is a tool to parse the Edits log file.


The NameNode uses a file in its local host OS file system to store the EditLog.

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HDFS - Checkpoint

During a checkpoint the changes from the transaction log (Editlog) are applied to the metadata store (FsImage) (because it's not efficient to record each change on the metadata store (FsImage) When...
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HDFS - File System Metadata

The file system metadata section of HDFS. The NameNode is the repository of all HDFS metadata. The metadata are stored in two files: fsimage file which is the metadata store EditLog transaction...
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The HDFS file system metadata are stored in a file called the FsImage. It contains: the entire file system namespace the mapping of blocks to files and file system properties The FsImage...
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HDFS - High Availibilty

The metadata files (FsImage and EditLog) are central data structures of HDFS. A corruption of these files can cause the HDFS instance to be non-functional. In a typical HA cluster: two separate...

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