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https://issues.apache.org/jira/browse/HADOOP-3232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12587795#action_12587795
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Raghu Angadi commented on HADOOP-3232:
--------------------------------------
What is the exact iostat command you ran? Is it an average over last 5 seconds
or so or overall average?
>From the data
{noformat}
2008-04-10 09:23:08,667 INFO org.apache.hadoop.dfs.DataNode: BlockReport of
497572 blocks got processed in 381086 msecs
{noformat}
A few things about this:
- You have around 500K blocks.. mostly of them very small (verification time is
very short). This is an order of magnitude larger than our datanodes have here
at Yahoo.
- The above log message says it too 6.5 min for block report. Most of this time
I would think is for listing the files in the local directory.
- Such a large number of blocks should cause similar problem with 0.15 also.
Anything you think is different?
Though DataNode should be able to handle larger number of blocks better, I
don't think this is a blocker for 0.16.3 release (unless iostat shows something
else). Do you agree?
Btw, are you planning to have large number of small blocks? Its going to limit
NameNode scalability.
> Datanodes time out
> ------------------
>
> Key: HADOOP-3232
> URL: https://issues.apache.org/jira/browse/HADOOP-3232
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.16.2
> Environment: 10 node cluster + 1 namenode
> Reporter: Johan Oskarsson
> Priority: Critical
> Fix For: 0.16.3
>
> Attachments: hadoop-hadoop-datanode-new.log,
> hadoop-hadoop-datanode-new.out, hadoop-hadoop-datanode.out,
> hadoop-hadoop-namenode-master2.out
>
>
> I recently upgraded to 0.16.2 from 0.15.2 on our 10 node cluster.
> Unfortunately we're seeing datanode timeout issues. In previous versions
> we've often seen in the nn webui that one or two datanodes "last contact"
> goes from the usual 0-3 sec to ~200-300 before it drops down to 0 again.
> This causes mild discomfort but the big problems appear when all nodes do
> this at once, as happened a few times after the upgrade.
> It was suggested that this could be due to namenode garbage collection, but
> looking at the gc log output it doesn't seem to be the case.
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