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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2791) WindowsDirectory
Date Fri, 03 Dec 2010 11:19:11 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2791?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12966489#action_12966489
] 

Uwe Schindler commented on LUCENE-2791:
---------------------------------------

bq. Also: this allows you to do the equivalent of Linux's O_DIRECT, right? If so... I think
we should augment the Dir API so that on opening an input it receives some sort of IOContext
or something expressing why we are opening. So for merging we would want "direct iO" (bypass
OS buffer cache or NOREUSE fadvise flag, etc.), and larger buffer sizes and perhaps other
low level IO settings in the future

Thats different to O_DIRECT. FS caches are still used by windows, but there are also options
to disable this: FILE_FLAG_WRITE_THROUGH [http://msdn.microsoft.com/en-us/library/aa363858(v=VS.85).aspx]

> WindowsDirectory
> ----------------
>
>                 Key: LUCENE-2791
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2791
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Store
>            Reporter: Robert Muir
>         Attachments: LUCENE-2791.patch, LUCENE-2791.patch, WindowsDirectory.dll, WindowsDirectory_amd64.dll
>
>
> We can use Windows' overlapped IO to do pread() and avoid the performance problems of
SimpleFS/NIOFSDir.

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