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https://issues.apache.org/jira/browse/HADOOP-692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12467104
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dhruba borthakur commented on HADOOP-692:
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+1 Code Reviewed.
One issue that came up in the code review was the persistence of Network
Topology in the case of namenode restart. Our consensus was to not persistently
store the network topology but require the namenode to reconstruct the network
topology upon restart.
> Rack-aware Replica Placement
> ----------------------------
>
> Key: HADOOP-692
> URL: https://issues.apache.org/jira/browse/HADOOP-692
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.8.0
> Reporter: Hairong Kuang
> Assigned To: Hairong Kuang
> Attachments: rack.patch, Rack_aware_HDFS_proposal.pdf
>
>
> This issue assumes that HDFS runs on a cluster of computers that spread
> across many racks. Communication between two nodes on different racks needs
> to go through switches. Bandwidth in/out of a rack may be less than the total
> bandwidth of machines in the rack. The purpose of rack-aware replica
> placement is to improve data reliability, availability, and network bandwidth
> utilization. The basic idea is that each data node determines to which rack
> it belongs at the startup time and notifies the name node of the rack id upon
> registration. The name node maintains a rackid-to-datanode map and tries to
> place replicas across racks.
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