sslug-teknik team mailing list archive

[Michael Rasmussen <mir@xxxxxxxxx>]

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On Wed, 13 Feb 2008 21:51:28 +0000 (UTC)
Jesper Krogh <jesper@xxxxxxxx> wrote:

> 
> Det passer jo ikke.. se nedenfor:
> 
Det er normalt en god ting at læse hele artiklen, inden man udtaler
sig:-)

"Reading a 16Mb file
time cat 16-meg-file > /dev/null

The results were astounding. data=journal mode allowed the 16-meg-file
to be read from 9 to over 13 times faster than other ext3 modes,
ReiserFS, and even ext2 (which has no journaling overhead):
Written-to-filesystem 	16-meg-read-time (seconds) ext2	78
ReiserFS	67 ext3 data=ordered 	93
ext3 data=writeback 	74
ext3 data=journal 	7

Andrew repeated this test, but tried to read a 16Mb file from the test
filesystem (rather than a different filesystem), and he got identical
results. So, what does this mean? Somehow, ext3's data=journal mode is
incredibly well-suited to situations where data needs to be read from
and written to disk at the same time. Therefore, ext3's data=journal
mode, which was assumed to be the slowest of all ext3 modes in nearly
all conditions, actually turns out to have a major performance
advantage in busy environments where interactive IO performance needs
to be maximized. Maybe data=journal mode isn't so sluggish after all!

Andrew is still trying to figure out exactly why data=journal mode is
doing so much better than everything else. When he does, he may be able
to add the necessary tweaks to the rest of ext3 so that data=writeback
and data=ordered modes see some benefit as well."

- -- 
Hilsen/Regards
Michael Rasmussen
http://keyserver.veridis.com:11371/pks/lookup?op=get&search=0xE3E80917
A computer is like air conditioning: it becomes useless when you open
windows.
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