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https://issues.apache.org/jira/browse/HDFS-9314?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15020408#comment-15020408
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Walter Su commented on HDFS-9314:
---------------------------------
Except the 2 replicas scenario [~mingma] mentioned, the changes to default
policy looks good to me.
1. Do you mind copy the old {{pickupReplicaSet}} logic to
{{BlockPlacementPolicyRackFaultTolerant}}? It still expects not to reduce rack
counts, as possible.
2. {{BlockPlacementPolicyWithNodeGroup}} prefers to pick nodes on the same
node-group. If no such nodes, the logic has no difference with the default
policy, before we change the default policy. So
{{BlockPlacementPolicyWithNodeGroup}} needs to be fixed too.
> Improve BlockPlacementPolicyDefault's picking of excess replicas
> ----------------------------------------------------------------
>
> Key: HDFS-9314
> URL: https://issues.apache.org/jira/browse/HDFS-9314
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ming Ma
> Assignee: Xiao Chen
> Attachments: HDFS-9314.001.patch, HDFS-9314.002.patch,
> HDFS-9314.003.patch, HDFS-9314.004.patch
>
>
> The test case used in HDFS-9313 identified NullPointerException as well as
> the limitation of excess replica picking. If the current replicas are on
> {SSD(rack r1), DISK(rack 2), DISK(rack 3), DISK(rack 3)} and the storage
> policy changes to HOT_STORAGE_POLICY_ID, BlockPlacementPolicyDefault's won't
> be able to delete SSD replica.
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