DRBD consists of two main components. The driver code in the kernel, and the user space tools to control, configure the driver, as well as integration programs and scripts that glues the DRBD system to cluster management software and other system components.
The driver code was developed for many years as so called out-of-tree module, and got integrated into the vanilla Linux kernel with the 2.6.33 release.
This means that if your Linux distribution is shipped with a kernel older than 2.6.33 you have to install a kernel module package and packages for the user land code. If you distribution contains a Linux-2.6.33 kernel or newer you only need to install the user land code.
Linux releases with DRBD
The following table shows the DRBD version equivalence relation between Linux releases and DRBD releases.
Please note that this table is not a recommendation of any kind, but merely states the facts of which in-tree DRBD source corresponds to which out-of-tree DRBD version.
Of course you can, and probably should, always upgrade to the latest DRBD module version by building the out-of-tree code, or installing the respective kernel module packages (see next page).
It is recommended to use userland packages of the same release as the kernel component.