Posts Tagged ‘barrier’

Confused about write barriers on file systems…

Sunday, November 1st, 2009

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…