[jira] [Updated] (HDFS-4945) A Distributed and Cooperative NameNode Cluster for a Highly-Available HDFS

["Suresh Srinivas (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-4945?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Suresh Srinivas updated HDFS-4945:
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    Description: See the following comment for detailed description.  (was: Recently, Hadoop attracts much attention of engineers and researchers as an emerging and effective framework for Big Data.
HDFS(Hadoop Distributed File System) can manage huge amount of data with guaranteeing high performance and reliability 
with only commodity hardware. 

However, HDFS requires a single master node, called NameNode, to manage the entire namespace (or all the i-nodes) 
of a file system. This causes SPOF (Single Point Of Failure) problem because the file system becomes inaccessible 
when the NameNode fails. (HDFS-2064)

This also causes a bottleneck of efficiency since all the access requests to the file system have to contact the 
NameNode. Hadoop 2.0 resolves the SPOF problem by introducing manual failover based on two NameNodes, Active and Standby.
However, it still has the efficiency bottleneck problem since all the access requests have to contact the Active 
in ordinary executions. It may also lose an advantage of using commodity hardware since the two NameNodes have to 
share a highly-reliable sophisticated storage.

We here propose a new HDFS architecture to resolve all the problems mentioned above.
The proposed architecture has the following features and advantages.

1. Multiple NameNodes (not restricted to two) can be utilized to improve availability.  
The entire namespace of a file system is partitioned into several fragments, and replicas of each fragment are 
dispersed among the NameNodes.  When each fragment has k replicas, the file system can tolerate up to 
floor(k/2 - 1) faulty NameNodes.

2. Multiple NameNodes can be utilized to improve performance. The performance bottleneck caused by a single 
NameNode can be circumvented by assigning different NameNodes to different fragments as the primary ones 
(or the entry points).

3. The highly-reliable storage shared by the NameNodes is removed by introducing message-based consistency 
mechanism among the NameNodes.  The architecture requires only commodity hardware.
)
    
> A Distributed and Cooperative NameNode Cluster for a Highly-Available HDFS
> --------------------------------------------------------------------------
>
>                 Key: HDFS-4945
>                 URL: https://issues.apache.org/jira/browse/HDFS-4945
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: auto-failover
>    Affects Versions: HA branch (HDFS-1623)
>            Reporter: Yonghwan Kim
>              Labels: documentation
>
> See the following comment for detailed description.

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