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https://issues.apache.org/jira/browse/HADOOP-8468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13288666#comment-13288666
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Robert Joseph Evans commented on HADOOP-8468:
---------------------------------------------

You can move the JIRAs.  More Actions -> Move.  If it is possible to split them 
up, it is nice to keep them separate, but it is not totally necessary.  If they 
do span multiple projects and are hard to split up you can leave them under 
HADOOP.  The main reason for this is that some people only watch the HDFS 
lists, while others only look at the MAPREDUCE lists, and may miss changes that 
are not filed under the appropriate group.

I am interested to see where this goes, and it seems very logical to me to be 
able to express to Hadoop what your topology really does look like.  I am not 
sure how many groups are running Hadoop inside VMs except perhaps on EC2, but I 
have a very limited view into that right now.
                
> Umbrella of enhancements to support different failure and locality topologies
> -----------------------------------------------------------------------------
>
>                 Key: HADOOP-8468
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8468
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ha, io
>    Affects Versions: 1.0.0, 2.0.0-alpha
>            Reporter: Junping Du
>            Assignee: Junping Du
>            Priority: Critical
>         Attachments: HADOOP-8468-total-v3.patch, HADOOP-8468-total.patch, 
> Proposal for enchanced failure and locality topologies.pdf
>
>
> The current hadoop network topology (described in some previous issues like: 
> Hadoop-692) works well in classic three-tiers network when it comes out. 
> However, it does not take into account other failure models or changes in the 
> infrastructure that can affect network bandwidth efficiency like: 
> virtualization. 
> Virtualized platform has following genes that shouldn't been ignored by 
> hadoop topology in scheduling tasks, placing replica, do balancing or 
> fetching block for reading: 
> 1. VMs on the same physical host are affected by the same hardware failure. 
> In order to match the reliability of a physical deployment, replication of 
> data across two virtual machines on the same host should be avoided.
> 2. The network between VMs on the same physical host has higher throughput 
> and lower latency and does not consume any physical switch bandwidth.
> Thus, we propose to make hadoop network topology extend-able and introduce a 
> new level in the hierarchical topology, a node group level, which maps well 
> onto an infrastructure that is based on a virtualized environment.

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