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https://issues.apache.org/jira/browse/HDFS-9807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997232#comment-15997232
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Virajith Jalaparti commented on HDFS-9807:
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Posted a new patch (v010) that reverts the unrelated changes to
{{Host2NodesMap}} and {{BlockPlacementPolicyDefault}} as [~chris.douglas]
pointed out. [~ehiggs], are you ok with this? The changes to those classes in
the earlier patches don't seem needed.
[~linyiqun] I think implementing a new {{VolumeChoosingPolicy}} will be one way
in which the Namenode's choice of the {{storageID}} is respected. As in the
comments above ([this |
https://issues.apache.org/jira/browse/HDFS-9807?focusedCommentId=15930679&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15930679]
and [this |
https://issues.apache.org/jira/browse/HDFS-9807?focusedCommentId=15929230&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15929230]),
it will be up to the {{VolumeChoosingPolicy}} to determine if the
{{storageID}} from the Namenode is used. For the choice of {{storageID}} to be
really respected, I think the {{BlockPlacementPolicy}} on the Namenode and the
{{VolumeChoosingPolicy}} should be consistent in the way the volumes are
chosen. The goal of this JIRA was to only provide the plumbing needed to
propagate the {{storageID}} to the {{VolumeChoosingPolicy}} and not to
implement a new {{VolumeChoosingPolicy}}. The actual policies to use can be
determined separately.
> 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, HDFS-9807.010.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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