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From "Hari Mankude (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4750) Support NFSv3 interface to HDFS
Date Thu, 25 Apr 2013 19:18:17 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4750?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642102#comment-13642102
] 

Hari Mankude commented on HDFS-4750:
------------------------------------

Implementing writes might not be easy. The client implementations in various kernels does
not guarantee that the writes are issued in sequential order. Page flushing algorithms try
to find contiguous pages (offsets). However, there are other factors in play with page flushing
algorithms.  So it does not imply that writes from the client has to be sequential as HDFS
requires it to be. This is true whether the writes are coming in lazily from the client or
due to a sync() before close(). A possible solution is for nfs gateway on dfs client to cache
and reorder the writes to be sequential. But, this might still result in "holes" which hdfs
cannot handle. Also, the cache requirements might not be trivial and might require a flush
to local disk.

NFS interfaces are very useful for reads. 
                
> Support NFSv3 interface to HDFS
> -------------------------------
>
>                 Key: HDFS-4750
>                 URL: https://issues.apache.org/jira/browse/HDFS-4750
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>    Affects Versions: 3.0.0
>            Reporter: Brandon Li
>            Assignee: Brandon Li
>         Attachments: HADOOP-NFS-Proposal.pdf
>
>
> Access HDFS is usually done through HDFS Client or webHDFS. Lack of seamless integration
with client’s file system makes it difficult for users and impossible for some applications
to access HDFS. NFS interface support is one way for HDFS to have such easy integration.
> This JIRA is to track the NFS protocol support for accessing HDFS. With HDFS client,
webHDFS and the NFS interface, HDFS will be easier to access and be able support more applications
and use cases. 
> We will upload the design document and the initial implementation. 

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