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https://issues.apache.org/jira/browse/HDFS-4750?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642068#comment-13642068
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Todd Lipcon commented on HDFS-4750:
-----------------------------------
{quote}
If the application expects that, after closing file through one NFS gateway,
the new data is immediately available to all other NFS gateways, the
application should do a sync call after close.
This is not a limitation only to this NFS implemtation. POSIX close doesn't
sync data implicitly.
{quote}
I don't think this is right. POSIX doesn't ensure that close() syncs data
(makes it durable), but NFS _does_ require that close() makes it _visible_ to
other clients (so-called "close-to-open consistency"):
{quote}
The NFS standard requires clients to maintain close-to-open cache coherency
when multiple clients access the same files [5, 6, 10]. This means flushing all
file data and metadata changes when a client closes a file, and immediately and
unconditionally retrieving a file's attributes when it is opened via the open()
system call API. In this way, changes made by one client appear as soon as a
file is opened on any other client.
{quote}
(from http://www.citi.umich.edu/projects/nfs-perf/results/cel/dnlc.html)
> 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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