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. DRBD also allows for user-defined block device names which must, however, start with drbd_.

[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. As of the time of this writing, each resource involves only two hosts and exactly one connection between these hosts, so for the most part, the terms resource and connection can be used interchangeably.

At the drbdadm level, a connection is addressed by the resource name.