Upgrading to DRBD 8.4
=====================

Linux kernel versions after 3.8 include DRBD 8.4, a new minor release with
significant changes both in configuration and operation. An overview of the
most important changes can be found at:

        http://www.drbd.org/users-guide-8.4/ap-recent-changes.html

Configuration file changes
--------------------------

A number of changes in the configuration file format are present in 8.4. They
are outlined at:

      http://www.drbd.org/users-guide-8.4/s-recent-changes-config.html

If you are upgrading from 8.3, please upgrade your configuration files to the
new format. Unfortunately, due to the way backwards compatility is provided
upstream, these options will not be understood by drbdadm if you boot a kernel
with DRBD 8.3 (kernel versions before 3.8), so you will have to revert your
changes if you want to use older kernels.

Downgrading to DRBD 8.3
------------------------

A device that has been attached or created using DRBD 8.4 will not work
automatically under DRBD 8.3, due to changes in device metadata. In order to
make your devices work with DRBD 8.3, you will have to do the following
*before* booting the old kernel, to ensure that the metadata is clean:

  drbdadm down all
  drbdadm apply-al all

More information can be found at:

       http://www.drbd.org/users-guide-8.4/s-downgrading-drbd84.html