1.4. Resource roles

In DRBD, every resource has a role, which may be Primary or Secondary.

[Note]Note

The choice of terms here is not arbitrary. These roles were deliberately not named "Active" and "Passive" by DRBD’s creators. Primary vs. secondary refers to a concept related to availability of storage, whereas active vs. passive refers to the availability of an application. It is usually the case in a high-availability environment that the primary node is also the active one, but this is by no means necessary.

The resource’s role can, of course, be changed, either by manual intervention or by way of some automated algorithm by a cluster management application. Changing the resource role from secondary to primary is referred to as promotion, whereas the reverse operation is termed demotion.