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From "Yuanbo Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11284) [SPS]: Avoid running SPS under safemode and fix issues in target node choosing.
Date Sun, 01 Jan 2017 04:29:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15790521#comment-15790521
] 

Yuanbo Liu commented on HDFS-11284:
-----------------------------------

[~umamaheswararao] Thanks for your response.
* The #2 issue seems to have been addressed in HDFS-11248 by [~rakeshr]. Sorry my branch didn't
contain the patch by then. But I'd like to explicate it a bit. Say we have these datanodes:
{code}
A => {disk, ssd}. B => {disk, archive}, C => {disk, archive}, D => {ssd, archive}
{code}
we set the file's storage policy to "COLD", the target assignment woule be {A => B, B =>
B, C => C}, because the {{chooseTargetTypeInSameNode}} doesn't have exclude list to avoid
adding the same node. 
* The #3 still exists. Say we have these datanodes in our cluster:
{code}
A => {disk, ssd}. B => {disk, archive}, C => {disk, archive}, D => {disk, archive}
{code}
Then we run these in our cluster:
1. create file and set the replication to 4
2. set the file's storage policy to "COLD"
3. change the replication to 3 and immediately satisfy the storage policy
4. in the end, not all the blocks of the file are moved correctly.
I have a thought on this issue. We can avoid assigning movement task if the file is under
replicated, and we need to add retry code if the movement fails.

> [SPS]: Avoid running SPS under safemode and fix issues in target node choosing.
> -------------------------------------------------------------------------------
>
>                 Key: HDFS-11284
>                 URL: https://issues.apache.org/jira/browse/HDFS-11284
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, namenode
>            Reporter: Yuanbo Liu
>            Assignee: Yuanbo Liu
>
> Recently I've found in some conditions, SPS is not stable:
> * SPS runs under safe mode.
> * There're some overlap nodes in the chosen target nodes.
> * The real replication number of block doesn't match the replication factor. For example,
the real replication is 2 while the replication factor is 3.



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