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List:       opensuse-factory
Subject:    Re: [opensuse-factory] Suggestions for ext3 filesystem in the YAST2 installer
From:       Adrian Schroeter <adrian () suse ! de>
Date:       2005-11-11 10:27:44
Message-ID: 200511111127.44640.adrian () suse ! de
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Hi,

can you make two bugreports with "enhancement" status out of this mail 
please ?

bye
adrian


On Friday 11 November 2005 11:13, jsiebert@arcor.de wrote:
> Hi there,
>
> i've been using ext3 as my favorite filesystem for all of my systems for
> some time now because of stability reasons (had some problems with xfs,
> reiserfs burns to many cpu cycles). Performance of ext3 in it's standard
> configuration on openSUSE/SUSE Linux 10 is not that good compared to
> reiserfs or xfs especially when it comes to write operations. So I've
> investigated the issue myself and found some things that could be improved
> in the future.
>
> 1. data=ordered vs. data=writeback on / filesystems.
>
> In ordered jounalling mode of ext3 data is always written to disk prior to
> the metadata (journal data). This ensures data consistency in most cases.
> However the performance of this option is not that well. In writeback
> journalling mode the metadata might get comitted to the journal before the
> data is actually written to the disk. This might lead to data corruption in
> some cases (e.g. power-off before the data could be written to disk but the
> journal data already has been commited). But on the other hand performance
> of this option is considerably better. The YAST2 installer allows to set
> the writeback  journalling mode but not in the / filesystem. I one
> specifies the data=writeback option in /etc/fstab the / filesystem is
> mounted in ordered journalling mode although. To get around this one can
> use the tune2fs tools with the option '-o journal_data_writeback'. This
> sets the default mount option for the filesystem with which it gets mounted
> in writeback journalling mode. The same applies to the 'journal'
> journalling mode.
>
> So my first suggestion for the YAST2 installer is to call' tune2fs -o
> journal_data_writeback' for the respective device if a user selects the
> writeback journalling mode on ext3 for the / filesystem. I've tested this
> on three different machines without any problems.
>
> 2. Enable dir_index feature
>
> ext3 has a feature called 'dir_index' which enables faster lookups in large
> filesystems by using a technique called hashed b-trees. Currently a user
> which wants to use this feature has to manually convert the filesystem by
> using 'tune2fs -O dir_index <device>' and 'fsck.ext3 -fD <device>' which
> takes a long time to complete on large filesystems. This feature can also
> be enabled by using 'mkfs.ext3 -O dir_index <device>' at filesystem
> creation time. The YAST2 installer doesn't offer an option for this.
>
> So my second suggestion is to add an option to the YAST2 installer to
> enable the dir_index feature at filesystem creation time. I've also tested
> this option on three different system and noticed some speedups especially
> on slower systems (my notebook).
>
> That's all for today ;-) Maybe these suggestions could be considered for
> future openSUSE/SUSE Linux releases.
>
> Greetings,
>
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-- 

Adrian Schroeter
SUSE Linux Products GmbH,  Maxfeldstr. 5, 90409 Nuernberg, Germany
email: adrian@suse.de


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