As ext3 is already known as a very robust file system why is the default mount option still barrier=0? The problem is LVM and the device mapper. They do not support barriers.
When mounting ext3 on a LV, the option barrier=1 it should be ignored and a warning written. So far so good. Trying this brings a lot of confusion. According to a Red Hat bugzilla entry one should get a warning, but no signs of that neither in /var/log/messages nor dmesg output. Even more confusing is the output of mount , it shows the LV is mounted with the barrier=1 option.
The conclusion is: Enable write barriers on physical disk-partitions brings a plus of reliability to your files system, on LVM setups it should better be disabled for the moment.
Is this fun? No…