Re: Direct IO In RH 3.0

On Sun, 29 Feb 2004 16:28:05 +0100, Frank van Bortel wrote:

> Lost in abbreviations here: JFS stands for Journalled File System, iirc.
> ext3 is a JFS, so you are saying ext3 does not support DIO, as it is
> JFS, which supports DIO.
> Does not make sense to me...
>
> I thought DIO was kernel 2.6 (maybe backported to 2.4x?)
>
> Please explain

JFS is IBM's file system, from AIX. Direct I/O is a low level I/O which is not very well supported and is usually ignored by many file systems (XFS reports an error). Ext2 does support direct I/O, but ext3 has had significant problems with it. The latest versions of ReiserFS no longer report an error woth it, while JFS works. Veritas charges significant amount of money for "Quick I/O" option, which is, essentially, ability to do direct I/O. JFS for linux is described at: http://www-124.ibm.com/jfs Direct I/O is an ability of the filesystem, and doesn't have much to do with kernel. I don't know about ext3 on 2.6 kernels, there may have been some improvements.

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