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https://issues.apache.org/jira/browse/HADOOP-4061?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12649525#action_12649525
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rangadi edited comment on HADOOP-4061 at 11/20/08 3:12 PM:
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(edit : correct jira number)
> I don't think we should redesign decommission feature here. Removing blocks
> will be a redesign.
hmm.. this is not done in the patch anyway. It does not look like redesign in
any way to me. It is fairly simple to me : if excess replica is on a normal DN,
it will be deleted (right?), then there is no reason to keep it if that happens
to be a decommissioned node. Alright, I noticed HADOOP-4701.
was (Author: rangadi):
> I don't think we should redesign decommission feature here. Removing
blocks will be a redesign.
hmm.. this is not done in the patch anyway. I does not look like redesign in
any way to me. It is fairly simple to me : if excess replica is on a normal DN,
it will be deleted (right?), then there is no reason to keep it if that happens
to be a decommissioned node. Alright, I noticed HADOOP-4071.
> Large number of decommission freezes the Namenode
> -------------------------------------------------
>
> Key: HADOOP-4061
> URL: https://issues.apache.org/jira/browse/HADOOP-4061
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.17.2
> Reporter: Koji Noguchi
> Assignee: Tsz Wo (Nicholas), SZE
> Attachments: 4061_20081119.patch, 4061_20081120.patch
>
>
> On 1900 nodes cluster, we tried decommissioning 400 nodes with 30k blocks
> each. Other 1500 nodes were almost empty.
> When decommission started, namenode's queue overflowed every 6 minutes.
> Looking at the cpu usage, it showed that every 5 minutes
> org.apache.hadoop.dfs.FSNamesystem$DecommissionedMonitor thread was taking
> 100% of the CPU for 1 minute causing the queue to overflow.
> {noformat}
> public synchronized void decommissionedDatanodeCheck() {
> for (Iterator<DatanodeDescriptor> it = datanodeMap.values().iterator();
> it.hasNext();) {
> DatanodeDescriptor node = it.next();
> checkDecommissionStateInternal(node);
> }
> }
> {noformat}
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