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From Arpit Agarwal <aagar...@hortonworks.com>
Subject Re: [VOTE] Merge HDFS-6581 to trunk - Writing to replicas in memory.
Date Tue, 30 Sep 2014 21:30:50 GMT
HDFS Devs,

The vote passes with 4 +1s (Jitendra, Jing, Suresh and mine), two -0s and
no binding vetoes. The branch will be merged to trunk by tomorrow.

Thank you to everyone who voted and provided feedback. The changes will be
merged to branch-2 when we have a resolution for the merge blocker raised
by Colin. This will also let the changes bake in trunk for a few days.


On Mon, Sep 22, 2014 at 5:24 PM, Arpit Agarwal <aagarwal@hortonworks.com>

> HDFS Devs,
> We propose merging the HDFS-6581 development branch to trunk.
> The work adds support to write to HDFS blocks in memory. The target use
> case covers applications writing relatively small, intermediate data sets
> with low latency. We introduce a new CreateFlag for the existing CreateFile
> API. HDFS will subsequently attempt to place replicas of file blocks in
> local memory with disk writes occurring off the hot path. The current
> design is a simplification of original ideas from Sanjay Radia on HDFS-5851.
> Key goals of the feature were minimal API changes to reduce application
> burden and best effort data durability. The feature is optional and
> requires appropriate DN configuration from administrators.
> Design doc:
> https://issues.apache.org/jira/secure/attachment/12661926/HDFSWriteableReplicasInMemory.pdf
> Test plan:
> https://issues.apache.org/jira/secure/attachment/12669452/Test-Plan-for-HDFS-6581-Memory-Storage.pdf
> There are 28 resolved sub-tasks under HDFS-6581, 3 open tasks for
> tests+Jenkins issues  and 7 open subtasks tracking planned improvements.
> The latest merge patch is 3300 lines of changed code of which 1300 lines is
> new and updated tests. Merging the branch to trunk will allow HDFS
> applications to start evaluating the feature. We will continue work on
> documentation, performance tuning and metrics in parallel with the vote and
> post-merge.
> Contributors to design and code include Xiaoyu Yao, Sanjay Radia, Jitendra
> Pandey, Tassapol Athiapinya, Gopal V, Bikas Saha, Vikram Dixit, Suresh
> Srinivas and Chris Nauroth.
> Thanks to Haohui Mai, Colin Patrick McCabe, Andrew Wang, Todd Lipcon, Eric
> Baldeschwieler and Vinayakumar B for providing useful feedback on
> HDFS-6581, HDFS-5851 and sub-tasks.
> The vote runs for the usual 7 days and will expire at 12am PDT on Sep 30.
> Here is my +1 for the merge.
> Regards,
> Arpit

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