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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Created: (HDFS-782) dynamic replication
Date Sat, 21 Nov 2009 01:09:39 GMT
dynamic replication

                 Key: HDFS-782
                 URL: https://issues.apache.org/jira/browse/HDFS-782
             Project: Hadoop HDFS
          Issue Type: New Feature
            Reporter: Ning Zhang

In a large and busy cluster, a block can be requested by many clients at the same time. HDFS-767
tries to solve the failing case when the # of retries exceeds the maximum # of retries. However,
that patch doesn't solve the performance issue since all failing clients have to wait a certain
period before retry, and the # of retries could be high. 

One solution to solve the performance issue is to increase the # of replicas for this "hot"
block dynamically when it is requested many times at a short period. The name node need to
be aware such situation and only clean up extra replicas when they are not accessed recently.

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