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Andrew Wang commented on HDFS-3702: ----------------------------------- Hey Eddy, thanks for reworking, a few comments: * Is BlockPlacementFlag being used in hadoop-common? Seems like it should go in hadoop-hdfs instead. * Can we name BlockPlacementFlag "AddBlockFlag" instead? That's more future-proof, since it doesn't restrict us to just BPP-related flags. * Can we hook into BlockPlacementPolicyDefault the same way as HDFS-4946? i.e. where the {{preferLocalNode}} boolean is used. It'd be good to implement these two features the same way, though it does require threading the state all the way down. * Nit: ClientProtocol "advice" -> "advise", though this might change after renaming to AddBlockFlag. > Add an option for NOT writing the blocks locally if there is a datanode on > the same box as the client > ----------------------------------------------------------------------------------------------------- > > Key: HDFS-3702 > URL: https://issues.apache.org/jira/browse/HDFS-3702 > Project: Hadoop HDFS > Issue Type: Improvement > Components: hdfs-client > Affects Versions: 2.5.1 > Reporter: Nicolas Liochon > Assignee: Lei (Eddy) Xu > Priority: Minor > Labels: BB2015-05-TBR > Attachments: HDFS-3702.000.patch, HDFS-3702.001.patch, > HDFS-3702.002.patch, HDFS-3702.003.patch, HDFS-3702.004.patch, > HDFS-3702.005.patch > > > This is useful for Write-Ahead-Logs: these files are writen for recovery > only, and are not read when there are no failures. > Taking HBase as an example, these files will be read only if the process that > wrote them (the 'HBase regionserver') dies. This will likely come from a > hardware failure, hence the corresponding datanode will be dead as well. So > we're writing 3 replicas, but in reality only 2 of them are really useful. -- This message was sent by Atlassian JIRA (v6.3.4#6332)