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https://issues.apache.org/jira/browse/HDFS-12725?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16225679#comment-16225679
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Wei-Chiu Chuang commented on HDFS-12725:
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Hi [~xiaochen] thanks for filing the jira and posting a patch.
A little nit in the debug message:
{code}
LOG.debug("Best effort placement failed.");
{code}
It might also be useful to log numResultsOflastChoose and totalReplicaExpected.
One question regarding the test code:
{code}
for (int i = 0; i <= numSingleDnRacks; i++) {
racks[i] = "/rack" + i;
}
for (int i = numSingleDnRacks + 1; i < numDatanodes; i++) {
racks[i] = "/rack" + (numSingleDnRacks + (i % (
numRacks - numSingleDnRacks)));
}
{code}
Can you explain why the first loop is between 0 <= i <= numSingleDnRacks? Why
isn't it between 0 <= i <numSingleDnRacks?
> BlockPlacementPolicyRackFaultTolerant still fails with racks with very few
> nodes
> --------------------------------------------------------------------------------
>
> Key: HDFS-12725
> URL: https://issues.apache.org/jira/browse/HDFS-12725
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: erasure-coding
> Affects Versions: 3.0.0
> Reporter: Xiao Chen
> Assignee: Xiao Chen
> Labels: hdfs-ec-3.0-must-do
> Attachments: HDFS-12725.01.patch, HDFS-12725.02.patch
>
>
> HDFS-12567 tries to fix the scenario where EC blocks may not be allocated in
> extremely rack-imbalanced cluster.
> The added fall-back step of the fix could be improved to do a best-effort
> placement. This is more likely to happen in testing than in real clusters.
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