On Tue, Aug 04, 2009 at 02:15:07AM +0300, Jari Aalto wrote:
>
> Manual page of mount(8), util-linux 2.15.1~rc1-1, reads
>
> Mount options for xfs
> barrier
>
> Enables the use of block layer write barriers for writes
> into the journal and unwritten extent conversion. This
> allows for drive level write caching to be enabled, for
> devices that support write barriers.
>
> <nothing more mentioned>
This text is from official XFS documentation (Linux kernel,
Documentation/filesystems/xfs.txt).
(Unfortunately, filesystems documentation is still mess. It would be
nice to have man page per filesystem and maintain all in kernel
tree. This topic has been discussed more times, but.... Volunteers? )
> However in article:
>
> "Barriers and journaling filesystems" 2008-05-21
> http://lwn.net/Articles/283161/
>
> ... ext3 and ext4 filesystems, by default, do not use barriers. The
> option is there, but, unless the administrator has explicitly
> requested the use of barriers, these filesystems operate without
> them - though some distributions (notably SUSE) change that default.
> ...
> So barriers are disabled by default because they have a serious
> impact on performance. And, beyond that, the fact is that people get
> away with running their filesystems without using barriers. Reports
> of ext3 filesystem corruption are few and far between.
>
> [Discussion]
> ...
> Posted May 21, 2008 14:17 UTC (Wed) by corbet (editor, #1)
> Some quick grepping on my kernel tree disk suggests that ext3 got
> the barrier option in 2.6.9.
>
> QUESTION
>
> Is the barrier option in the current 2.6.x kernels as mentioned? If it
> is could someone document it to the manual page according to the
> article.
CC: too linux-xfs ML.
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
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