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https://issues.apache.org/jira/browse/HDFS-8461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14556655#comment-14556655
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Zhe Zhang commented on HDFS-8461:
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HDFS-8010 patch (note that the rename part has been committed as HDFS-8255)
adds a unified method to represent the preferred number of storage locations.
But I'm OK with the method in this patch with 2 {{getPriority}} methods. Will
post my review soon.
> Erasure coding: fix priority level of UnderReplicatedBlocks for striped block
> -----------------------------------------------------------------------------
>
> Key: HDFS-8461
> URL: https://issues.apache.org/jira/browse/HDFS-8461
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Walter Su
> Assignee: Walter Su
> Attachments: HDFS-8461-HDFS-7285.001.patch
>
>
> {code:title=UnderReplicatedBlocks.java}
> private int getPriority(int curReplicas,
> ...
> } else if (curReplicas == 1) {
> //only on replica -risk of loss
> // highest priority
> return QUEUE_HIGHEST_PRIORITY;
> ...
> {code}
> For stripe blocks, we should return QUEUE_HIGHEST_PRIORITY when curReplicas
> == 6( Suppose 6+3 schema).
> That's important. Because
> {code:title=BlockManager.java}
> DatanodeDescriptor[] chooseSourceDatanodes(BlockInfo block,
> ...
> if(priority != UnderReplicatedBlocks.QUEUE_HIGHEST_PRIORITY
> && !node.isDecommissionInProgress()
> && node.getNumberOfBlocksToBeReplicated() >= maxReplicationStreams)
> {
> continue; // already reached replication limit
> }
> ...
> {code}
> It may return not enough source DNs ( maybe 5), and failed to recover.
> A busy node should not be skiped if a block has highest risk/priority. The
> issue is the striped block doesn't have priority.
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