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Posted to hdfs-issues@hadoop.apache.org by "Lukas Majercak (JIRA)" <ji...@apache.org> on 2018/03/15 20:30:00 UTC
[jira] [Work started] (HDFS-13284) Adjust criteria for
LowRedundancyBlocks.QUEUE_VERY_LOW_REDUNDANCY
[ https://issues.apache.org/jira/browse/HDFS-13284?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Work on HDFS-13284 started by Lukas Majercak.
---------------------------------------------
> Adjust criteria for LowRedundancyBlocks.QUEUE_VERY_LOW_REDUNDANCY
> -----------------------------------------------------------------
>
> Key: HDFS-13284
> URL: https://issues.apache.org/jira/browse/HDFS-13284
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs, namenode
> Reporter: Lukas Majercak
> Assignee: Lukas Majercak
> Priority: Major
> Attachments: HDFS-13284.000.patch
>
>
> LowRedundancyBlocks currently has 5 priority queues:
> QUEUE_HIGHEST_PRIORITY = 0 - reserved for last replica blocks
> QUEUE_VERY_LOW_REDUNDANCY = 1 - *if ((curReplicas * 3) < expectedReplicas)*
> QUEUE_LOW_REDUNDANCY = 2 - the rest
> QUEUE_REPLICAS_BADLY_DISTRIBUTED = 3
> QUEUE_WITH_CORRUPT_BLOCKS = 4
> The problem lies in QUEUE_VERY_LOW_REDUNDANCY. Currently, a block that has curReplicas=2 and expectedReplicas=4 is treated the same as a block with curReplicas=3 and expectedReplicas=4. A block with 2/3 replicas is also put into QUEUE_LOW_REDUNDANCY.
> The proposal is to change the *{{if ((curReplicas * 3) < expectedReplicas)}}* check to *{{if ((curReplicas * 2) <= expectedReplicas || curReplicas == 2)}}*
>
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