I've seen this question asked before, but nobody has ever had an answer. I'm hoping someone can help me figure out how to mount the root filesystem on an ext3 partition using the writeback journaling method. I know it's technically not the best for data integrity, but the speed hit on our database server is just too large using the ordered method. So I wanted to try using the writeback method, as it's supposed to be a lot faster. But everytime I try to add the data=writeback to my /etc/fstab file, I get all kinds of read errors on bootup (read-only filesystem errors) and have to reboot and then recover. Here's what I've been trying:

My original fstab file for root looks like this:

LABEL=/ / ext3 defaults 1 1

I've been trying to change it to this:

LABEL=/ / ext3 data=writeback 1 1

Another thread suggested adding the "noatime" value as well, but didn't go into how to get it set up, and I can't seem to find any examples of someone actually using it. So, can anyone help out with this, as I'd really like to see if either of these will make a difference in my speeds.

Thanks.

Edit: I think I have the "noatime" option working.. just replaced the 'defaults' option with 'noatime' and it seemed to take. I'd still like to try the data=writeback option though if someone knows how to get it working.

I have no idea about the writeback issue, but here is an example of two partitions on my system which have noatime in use:

/dev/hde1 /boot reiserfs noatime,notail 1 1
/dev/root / reiserfs noatime 0 0

Thanks for the examples, I think it's working ok with the noatime options. Is there an easy way to verify this?

Also, I did get the writeback mode set properly on my root partition... it's just not as easy as it should be. Basically, here's what you need to do:

1. Modify the /etc/fstab file. In place of defaults, I put in data=writeback,noatime

2. Run mkinitrd and create a new image file

3. Modify the grub.conf (or lilo) file to point to the new image file.

Apparently, if you just change the fstab file without doing the rest, it is in effect trying to remount the filesystem, but for some reason (bug?), it's not able to remount it with write access, so booting always fails. I tried it the way I specified twice (2 different kernel versions), and I saw during the boot process that it set journaling to writeback mode. Now to test it and see what kind of performance I get...

Thanks for the help!