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https://issues.apache.org/jira/browse/HDFS-6581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14143872#comment-14143872
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Arpit Agarwal commented on HDFS-6581:
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Suresh, good suggestions. Let me file a task for metrics. A few other metrics I
have been thinking of:
# Number of blocks written to memory
# Number of memory writes requested but not satisfied (failed-over to disk)
# Number of blocks evicted without ever being read from memory
# Average delay between memory write and disk write (window where a node
restart could cause data loss).
It might be also useful to track how often a block was requested to be read
shortly after eviction, however that requires more overhead to track.
We can do this work 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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