Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 493

Ext3 in the data=journal mode offers maximum security (data integrity), but
can slow down the system because both metadata and data are journaled. A rela-
tively new approach is to use the data=ordered mode, which ensures both data
and metadata integrity, but uses journaling only for metadata. The file system
driver collects all data blocks that correspond to one metadata update. These data
blocks are written to disk before the metadata is updated. As a result, consistency
is achieved for metadata and data without sacrificing performance. A third option
to use is data=writeback, which allows data to be written into the main file
system after its metadata has been committed to the journal. This option is often
considered the best in performance. It can, however, allow old data to reappear in
files after crash and recovery while internal file system integrity is maintained.
Unless you specify something else, Ext3 is run with the data=ordered default.
25.2.4 Converting an Ext2 File System into
Ext3
To convert an Ext2 file system to Ext3, proceed as follows:
1 Create an Ext3 journal by running tune2fs -j as root. This creates an Ext3
journal with the default parameters.
To decide yourself how large the journal should be and on which device it should
reside, run tune2fs -J instead together with the desired journal options
size= and device=. More information about the tune2fs program is available
in the tune2fs manual page.
2 To ensure that the Ext3 file system is recognized as such, edit the file /etc/
fstab as root, changing the file system type specified for the corresponding
partition from ext2 to ext3. The change takes effect after the next reboot.
3 To boot a root file system set up as an Ext3 partition, include the modules ext3
and jbd in the initrd. To do this, edit /etc/sysconfig/kernel as
root, adding ext3 and jbd to the INITRD_MODULES variable. After saving
the changes, run the mkinitrd command. This builds a new initrd and prepares
it for use.
File Systems in Linux 475