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https://issues.apache.org/jira/browse/HDFS-9807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15996319#comment-15996319
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Ewan Higgs commented on HDFS-9807:
----------------------------------
{quote}The changes to Host2NodesMap and BlockPlacementPolicyDefault are
unrelated?{quote}
The change to {{Host2NodesMap}} were from when I tried to add a custom
{{BlockPlacementPolicy}} based on the top level abstract class. This requires
overloading {{initialize}} which uses {{Host2NodesMap}} as an argument:
{code}
protected abstract void initialize(Configuration conf, FSClusterStats stats,
NetworkTopology clusterMap,
Host2NodesMap host2datanodeMap);
{code}
[~virajith] chose the superior solution of merely extending
{{BlockPlacementPolicyDefault}} which already implements {{initialize}}. FWIW,
if {{BlockPlacementPolicy}} is public then all types used in the interface
should probably also be public.
Re: {{BlockPlacementPolicyDefault}} changes, yes those are unrelated whitespace
changes.
> 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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