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Message-ID: <4A80894A.7050506@redhat.com> Date: Mon, 10 Aug 2009 16:55:38 -0400 From: Ric Wheeler <rwheeler@...hat.com> To: "Theodore Ts'o" <tytso@....edu> CC: Jan Kara <jack@...e.cz>, Linux Kernel Developers List <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org Subject: Re: [PATCH, RFC] ext3: Update Kconfig description of EXT3_DEFAULTS_TO_ORDERED On 08/10/2009 04:03 PM, Theodore Ts'o wrote: > The old description for this configuration option was perhaps not > completely balanced in terms of describing the tradeoffs of using a > default of data=writeback vs. data=ordered. Despite the fact that old > description very strongly recomended disabling this feature, all of > the major distributions have elected to preserve the existing 'legacy' > default, which is a strong hint that it perhaps wasn't telling the > whole story. > > This revised description has been vetted by a number of ext3 > developers as being better at informing the user about the tradeoffs > of enabling or disabling this configuration feature. > > Signed-off-by: "Theodore Ts'o"<tytso@....edu> > Cc: linux-ext4@...r.kernel.org > Thanks Ted - this is much more informative and will allow for a more informed trade off to be made, Ric > --- > fs/ext3/Kconfig | 32 +++++++++++++++++--------------- > 1 files changed, 17 insertions(+), 15 deletions(-) > > diff --git a/fs/ext3/Kconfig b/fs/ext3/Kconfig > index fb3c1a2..522b154 100644 > --- a/fs/ext3/Kconfig > +++ b/fs/ext3/Kconfig > @@ -29,23 +29,25 @@ config EXT3_FS > module will be called ext3. > > config EXT3_DEFAULTS_TO_ORDERED > - bool "Default to 'data=ordered' in ext3 (legacy option)" > + bool "Default to 'data=ordered' in ext3" > depends on EXT3_FS > help > - If a filesystem does not explicitly specify a data ordering > - mode, and the journal capability allowed it, ext3 used to > - historically default to 'data=ordered'. > - > - That was a rather unfortunate choice, because it leads to all > - kinds of latency problems, and the 'data=writeback' mode is more > - appropriate these days. > - > - You should probably always answer 'n' here, and if you really > - want to use 'data=ordered' mode, set it in the filesystem itself > - with 'tune2fs -o journal_data_ordered'. > - > - But if you really want to enable the legacy default, you can do > - so by answering 'y' to this question. > + The journal mode options for ext3 have different tradeoffs > + between when data is guaranteed to be on disk and > + performance. The use of "data=writeback" can cause > + unwritten data to appear in files after an system crash or > + power failure, which can be a security issue. However, > + "data=ordered" mode can also result in major performance > + problems, including seconds-long delays before an fsync() > + call returns. For details, see: > + > + http://ext4.wiki.kernel.org/index.php/Ext3_data_mode_tradeoffs > + > + If you have been historically happy with ext3's performance, > + data=ordered mode will be a safe choice and you should > + answer 'y' here. If you understand the reliability and data > + privacy issues of data=writeback and are willing to make > + that trade off, answer 'n'. > > config EXT3_FS_XATTR > bool "Ext3 extended attributes" > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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