Re: Asking about Unbuffer I/O in linux

Alan Cox (alan@lxorguk.ukuu.org.uk)
Fri, 15 Oct 1999 20:23:33 +0100 (BST)

> I met a problem which need me to use unbuffered I/O in linux. The problem
> is related to hard disk I/O.
> When I read from the Linux buffer cache, the other system may write new
> data to the hard disk, while
> the Linux buffer cache doesnot know it. So I try to find if there are some
> methods to disable the buffer

Stephen Tweedie did some 2.2.x patches to allow you to do direct uncached
I/O to and from the media. The typical application for this being things like
clustered database with shared disk.

If you want to do this with a file system not raw disk however you will need
to do a lot more work. File systems don't expect multiple writer machines -
although a project called GFS is working on a fibrechannel based fs that
does

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