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https://issues.apache.org/jira/browse/HDFS-6581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14143865#comment-14143865
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Suresh Srinivas commented on HDFS-6581:
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bq. I think system-level testing will be needed. I think it's fine to merge
without this system-level testing being done
To understand how effective memory tier is, and also to be able to tell the
difference between different pluggable implementations, we may need good set of
metrics. What should those metrics be? Some early thoughts:
- Number of times a block in memory was read (before being ejected)
- Average block size for data written to memory tier
- Time the block was in memory before being ejected
We probably will continue to add metrics based on use cases. We can start by
adding some metrics we think are useful. This work can happen in trunk.
> Write to single replica in memory
> ---------------------------------
>
> Key: HDFS-6581
> URL: https://issues.apache.org/jira/browse/HDFS-6581
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: HDFS-6581.merge.01.patch, HDFS-6581.merge.02.patch,
> HDFS-6581.merge.03.patch, HDFS-6581.merge.04.patch, HDFS-6581.merge.05.patch,
> HDFS-6581.merge.06.patch, HDFS-6581.merge.07.patch, HDFS-6581.merge.08.patch,
> HDFS-6581.merge.09.patch, HDFSWriteableReplicasInMemory.pdf,
> Test-Plan-for-HDFS-6581-Memory-Storage.pdf
>
>
> Per discussion with the community on HDFS-5851, we will implement writing to
> a single replica in DN memory via DataTransferProtocol.
> This avoids some of the issues with short-circuit writes, which we can
> revisit at a later time.
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