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From "Brandon Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6549) Add support for accessing the NFS gateway from the AIX NFS client
Date Wed, 18 Jun 2014 22:48:25 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6549?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14036589#comment-14036589

Brandon Li commented on HDFS-6549:

Guess AIX NFS server doesn't put mtime in the verifier and uses it in a different way.  :-)

The patch should be able to fix the AIX NFS client problems. The only thing is that, the aix.compatibility.mode
should not be recommended for non AIX client for the following reasons:
1. NFS client considers it's safe to clear the buffer cache as long as the data is committed.
In aix.compatibility.mode, NFS could returns commit success even when the data is not received.

2. Many NFS clients restart directory listing once it encounters verifier mismatch error.
In aix.compatibility.mode, client may not get the most recent directory content.

> Add support for accessing the NFS gateway from the AIX NFS client
> -----------------------------------------------------------------
>                 Key: HDFS-6549
>                 URL: https://issues.apache.org/jira/browse/HDFS-6549
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: nfs
>    Affects Versions: 2.4.0
>            Reporter: Aaron T. Myers
>            Assignee: Aaron T. Myers
>         Attachments: HDFS-6549.patch
> We've identified two issues when trying to access the HDFS NFS Gateway from an AIX NFS
> # In the case of COMMITs, the AIX NFS client will always send 4096, or a multiple of
the page size, for the offset to be committed, even if fewer bytes than this have ever, or
will ever, be written to the file. This will cause a write to a file from the AIX NFS client
to hang on close unless the size of that file is a multiple of 4096.
> # In the case of READDIR and READDIRPLUS, the AIX NFS client will send the same cookie
verifier for a given directory seemingly forever after that directory is first accessed over
NFS, instead of getting a new cookie verifier for every set of incremental readdir calls.
This means that if a directory's mtime ever changes, the FS must be unmounted/remounted before
readdir calls on that dir from AIX will ever succeed again.
> From my interpretation of RFC-1813, the NFS Gateway is in fact doing the correct thing
in both cases, but we can introduce simple changes on the NFS Gateway side to be able to optionally
work around these incompatibilities.

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