There are three mode for ext3 journal:
1) journal
2) journal ordered
3) journal writeback
By default, the linux distribution use 'ordered' mode. However it's better to use 'writeback' mode if there are many system disk IO.
Here is the steps:
1) edit /etc/fstab, append 'data=writeback'. That will be:
LABEL=/ / ext3 defaults,data=writeback 1 1
2) edit /boot/grub/menu.lst, append 'rootflags=data=writeback' in boot option. That will be:
kernel /boot/vmlinuz-2.6.18-243.el5 ro root=LABEL=/ ide0=noprobe rhgb quiet rootflags=data=writeback
3) IMPORTANT: adjust tunable filesystem parameters.
tune2fs -o journal_data_writeback /dev/hda1
OK, It's done! reboot the system, use this command to check the result:
dmesg | grep mode
This message should be there:
...
EXT3-fs: mounted filesystem with writeback data mode.
...
or use tune2fs -l /dev/hda1
if step 3 is missing (actually I did go to the wrong way), the root filesystem maybe read-only. you can remount the root filesystme use this commnad:
mount -n -o remount /
