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https://issues.apache.org/jira/browse/HDFS-13573?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yiqun Lin updated HDFS-13573:
-----------------------------
Description:
Current rule of default block placement policy:
{quote}The replica placement strategy is that if the writer is on a datanode,
the 1st replica is placed on the local machine,
otherwise a random datanode. The 2nd replica is placed on a datanode
that is on a different rack. The 3rd replica is placed on a datanode
which is on a different node of the rack as the second replica.
{quote}
*if the writer is on a datanode, the 1st replica is placed on the local
machine*, actually this can be decided by the hdfs client. The client can pass
{{CreateFlag#NO_LOCAL_WRITE}} that request to not put a block replica on the
local datanode. But subsequent replicas will still follow default block
placement policy.
was:
Current rule of default block placement:
{quote}
The replica placement strategy is that if the writer is on a datanode,
the 1st replica is placed on the local machine,
otherwise a random datanode. The 2nd replica is placed on a datanode
that is on a different rack. The 3rd replica is placed on a datanode
which is on a different node of the rack as the second replica.
{quote}
> Javadoc for BlockPlacementPolicyDefault is inaccurate
> -----------------------------------------------------
>
> Key: HDFS-13573
> URL: https://issues.apache.org/jira/browse/HDFS-13573
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.1.0
> Reporter: Yiqun Lin
> Priority: Trivial
>
> Current rule of default block placement policy:
> {quote}The replica placement strategy is that if the writer is on a datanode,
> the 1st replica is placed on the local machine,
> otherwise a random datanode. The 2nd replica is placed on a datanode
> that is on a different rack. The 3rd replica is placed on a datanode
> which is on a different node of the rack as the second replica.
> {quote}
> *if the writer is on a datanode, the 1st replica is placed on the local
> machine*, actually this can be decided by the hdfs client. The client can
> pass {{CreateFlag#NO_LOCAL_WRITE}} that request to not put a block replica on
> the local datanode. But subsequent replicas will still follow default block
> placement policy.
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