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https://issues.apache.org/jira/browse/HDFS-9807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997038#comment-15997038
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Yiqun Lin commented on HDFS-9807:
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Thanks [~ehiggs] for the working on this. It's a nice work! I take a quick look
on this and just have some questions.
For the interface of VolumeChoosingPolicy#chooseVolume, how to decide if it
should respect the storageID chosen from namenode or just ignore this? A new
setting to control this?
In addition, if VolumeChoosingPolicy can respect the chosen from namenode after
this patch, is that mean we should Improve the selection in choosing storage
for blocks that did in {{DatanodeDescriptor#chooseStorage4Block}}. Under the
currently logic, it will always return the first valid storage for block
writing, I have did this improvement in HDFS-11464. I think that JIRA should be
reopened and will make sense now, right?
Thanks for the any comments.
> Add an optional StorageID to writes
> -----------------------------------
>
> Key: HDFS-9807
> URL: https://issues.apache.org/jira/browse/HDFS-9807
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 3.0.0-alpha2
> Reporter: Chris Douglas
> Assignee: Ewan Higgs
> Attachments: HDFS-9807.001.patch, HDFS-9807.002.patch,
> HDFS-9807.003.patch, HDFS-9807.004.patch, HDFS-9807.005.patch,
> HDFS-9807.006.patch, HDFS-9807.007.patch, HDFS-9807.008.patch,
> HDFS-9807.009.patch
>
>
> The {{BlockPlacementPolicy}} considers specific storages, but when the
> replica is written the DN {{VolumeChoosingPolicy}} is unaware of any
> preference or constraints from other policies affecting placement. This
> limits heterogeneity to the declared storage types, which are treated as
> fungible within the target DN. It should be possible to influence or
> constrain the DN policy to select a particular storage.
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