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From "Robert Chansler (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-3215) Save (sync) journal (fsimage) to alternate/secondary/read-only name node
Date Tue, 08 Apr 2008 23:11:27 GMT
Save (sync) journal (fsimage) to alternate/secondary/read-only name node

                 Key: HADOOP-3215
                 URL: https://issues.apache.org/jira/browse/HADOOP-3215
             Project: Hadoop Core
          Issue Type: New Feature
          Components: dfs
            Reporter: Robert Chansler

The name node journal records HDFS transactions. The journal can be written to multiple file
systems (but not HDFS itself!) to increase the durability of the journal. The transaction
has to wait for each copy to sync. If one of the file systems becomes slow, performance of
HDFS is affected. 

As an alternative to directly writing a remote file, the transaction could be written to another
name node. The alternate node could be the secondary name node, or a read-only name node replica
that provides a journal service. The idea being that receipt of the record--but not its sync
to the local disk--would be good enough as a journal replica. This could provide a fast, predictable
journal replica where common-mode failures are sufficiently improbable or tolerable.


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