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https://issues.apache.org/jira/browse/HDFS-8392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14555264#comment-14555264
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Arpit Agarwal commented on HDFS-8392:
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The attached patch is the first step to supporting alternate Dataset
implementations. This fixes assumptions in the DataNode code that there is a
single dataset instance. Instead the block pool Id is used to lookup the
dataset. The dataset instantiation is keyed off the service type, so all
federated block pools would share the same dataset instance.
I left {{Datanode#data}} and {{Datanode#getFSDataset}} to avoid massive changes
to existing test cases and tagged them {{@VisibleForTesting}}. For HDFS unit
tests we will never have more than one dataset instance.
> DataNode support for multiple datasets
> --------------------------------------
>
> Key: HDFS-8392
> URL: https://issues.apache.org/jira/browse/HDFS-8392
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: HDFS-8392-HDFS-7240.01.patch
>
>
> For HDFS-7240 we would like to share available DataNode storage across HDFS
> blocks and Ozone objects.
> The DataNode already supports sharing available storage across multiple block
> pool IDs for the federation feature. However all federated block pools use
> the same dataset implementation i.e. {{FsDatasetImpl}}.
> We can extend the DataNode to support multiple dataset implementations so the
> same storage space can be shared across one or more HDFS block pools and one
> or more Ozone block pools.
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