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https://issues.apache.org/jira/browse/HDFS-9806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16118654#comment-16118654
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Sean Mackrory commented on HDFS-9806:
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Could someone more familiar with the design here comment on any anticipated
impact to NameNode scalability? If this feature is included but a user chooses
not to use it (i.e. there are no storages of type PROVIDED) - is there any
impact to memory consumed by the NameNode? I've read the design doc and some of
the patches - I *think* things are good but wanting to be sure by someone more
familiar with the implementation and who might have even tested that already...
> Allow HDFS block replicas to be provided by an external storage system
> ----------------------------------------------------------------------
>
> Key: HDFS-9806
> URL: https://issues.apache.org/jira/browse/HDFS-9806
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Chris Douglas
> Attachments: HDFS-9806-design.001.pdf, HDFS-9806-design.002.pdf
>
>
> In addition to heterogeneous media, many applications work with heterogeneous
> storage systems. The guarantees and semantics provided by these systems are
> often similar, but not identical to those of
> [HDFS|https://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/filesystem/index.html].
> Any client accessing multiple storage systems is responsible for reasoning
> about each system independently, and must propagate/and renew credentials for
> each store.
> Remote stores could be mounted under HDFS. Block locations could be mapped to
> immutable file regions, opaque IDs, or other tokens that represent a
> consistent view of the data. While correctness for arbitrary operations
> requires careful coordination between stores, in practice we can provide
> workable semantics with weaker guarantees.
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