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Posted to common-dev@hadoop.apache.org by "Bryan Pendleton (JIRA)" <ji...@apache.org> on 2006/08/08 00:22:14 UTC
[jira] Created: (HADOOP-429) Periodically move blocks from full
nodes to those with space
Periodically move blocks from full nodes to those with space
-------------------------------------------------------------
Key: HADOOP-429
URL: http://issues.apache.org/jira/browse/HADOOP-429
Project: Hadoop
Issue Type: Improvement
Reporter: Bryan Pendleton
Continuance of Hadoop-386. The patch to that issue makes it possible to redistribute blocks (change replication up, wait for replication to succeed, then lower replication again). However, this requires a lot more space, is not automatic, and doesn't respect a reasonable I/O limit. I have actually had MapReduce jobs fail from block missing execptions after having recently changed the replication level (from 3 to 4, with no underreplications to start with) because the datanodes were too slow responding to requests while performing the necessary replications.
A good fix to this problem would be a low-priority thread on the NameNode that schedules low-priority replications of blocks on over-full machines, followed by the removal of the extra replications. It might be worth having a specific prototocol for asking for these low-priority copies to happen in the datanodes, so that they continue to service (and be available to service) normal block requests.
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[jira] Updated: (HADOOP-429) Periodically move blocks from full
nodes to those with space
Posted by "Sameer Paranjpye (JIRA)" <ji...@apache.org>.
[ http://issues.apache.org/jira/browse/HADOOP-429?page=all ]
Sameer Paranjpye updated HADOOP-429:
------------------------------------
Component/s: dfs
> Periodically move blocks from full nodes to those with space
> -------------------------------------------------------------
>
> Key: HADOOP-429
> URL: http://issues.apache.org/jira/browse/HADOOP-429
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Reporter: Bryan Pendleton
>
> Continuance of Hadoop-386. The patch to that issue makes it possible to redistribute blocks (change replication up, wait for replication to succeed, then lower replication again). However, this requires a lot more space, is not automatic, and doesn't respect a reasonable I/O limit. I have actually had MapReduce jobs fail from block missing execptions after having recently changed the replication level (from 3 to 4, with no underreplications to start with) because the datanodes were too slow responding to requests while performing the necessary replications.
> A good fix to this problem would be a low-priority thread on the NameNode that schedules low-priority replications of blocks on over-full machines, followed by the removal of the extra replications. It might be worth having a specific prototocol for asking for these low-priority copies to happen in the datanodes, so that they continue to service (and be available to service) normal block requests.
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