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Re: converting / to ext3-0.0.5d



Joachim, you write:
> again I ran into some difficulties while setting up my / - partition 
> under v0.0.5.
> 
> With the conversion of my /home - partition went everything well.
> Even under heavy load  I didn't remark anything unusal - apart from a 
> little performance-issue.
> 
> My current setup is now the following:
> 
> / - partition: no conversion possible: V1-journal with journal-data mode
> /home - partition: conversion from V1 to V2: V2-journal with 
> ordered-data mode
> 
> How can I convert my /-partition from V1 to V2?

For existing filesystems, you need to use the "journal=update" option
to update the journal format.  For root, can do this with a boot parameter
at the LILO boot prompt (assuming linux is the name of your kernel):

linux rootflags=journal=update

> Which mode is faster - journal- or ordered-mode?

Ordered mode is considerably faster, which is why it is the default.
With "journalled data" mode, all of the data written to a file is actually
written to disk twice - once to the journal, and a second time to the
place on disk where it really belongs.  With ordered mode, it is only
written to disk once - where it belongs - but only when the metadata is
finished writing to the journal.  From my testing, ordered mode is nearly
the same speed as ext2 for bonnie++ block I/O tests, but of course still
slower for file creation/deletion because these need to be journalled.

There is also a third mode - "writeback data" which lets the flush daemon
write it to disk whenever it wants.  This actually turns out to be slower
in my testing (as with Stephen's testing).  He speculates that this is
because the kjournald and kflushd are writing to different parts of the
disk which and the seeking slows things down.

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert





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