1.3. Resources

In DRBD, resource is the collective term that refers to all aspects of a particular replicated data set. These include:

Resource name. This can be any arbitrary, US-ASCII name not containing whitespace by which the resource is referred to.

Volumes. Any resource is a replication group consisting of one of more volumes that share a common replication stream. DRBD ensures write fidelity across all volumes in the resource. Volumes are numbered starting with 0, and there may be up to 65,535 volumes in one resource. A volume contains the replicated data set, and a set of metadata for DRBD internal use.

At the drbdadm level, a volume within a resource can be addressed by the resource name and volume number as resource/volume.

DRBD device. This is a virtual block device managed by DRBD. It has a device major number of 147, and its minor numbers are numbered from 0 onwards, as is customary. Each DRBD device corresponds to a volume in a resource. The associated block device is usually named /dev/drbdX, where X is the device minor number. udev will typically also create symlinks containing the resource name and volume number, as in /dev/drbd/by-res/resource/vol-nr.

[Note]Note

Very early DRBD versions hijacked NBD’s device major number 43. This is long obsolete; 147 is the LANANA-registered DRBD device major.

Connection. A connection is a communication link between two hosts that share a replicated data set. With DRBD 9 each resource can be defined on multiple hosts; with the current versions this requires a full-meshed connection setup between these hosts (ie. each host connected to every other for that resource)

At the drbdadm level, a connection is addressed by the resource and the connection name (the latter defaulting to the peer hostname), like resource:connection.