The DRBD kernel driver presents virtual block devices to the system. It is an important building block of the DRBD SDS. It reads and writes data to optional local backing devices.
The DRBD kernel driver mirrors data writes to one (or multiple) peer(s). In synchronous mode it will signal completion of a write request after it receives completion events from the local backing storage device and from the peer(s).
The illustration on the left shows the path the data takes within the DRBD kernel driver. Please note that the data path is very efficient. No user space components involved. Read requests can be carried out locally, not causing network traffic.
Since version 9.0, DRBD has an abstraction for network transport implementations. Before 9.0, TCP was the only built-in option.
TCP/IP is the natural choice. It is the protocol of the Internet. Usually it is used on top of ethernet hardware (NICs and switches) in the data center. While it is the lingua franca of the network it has started to become outdated and is not the best choice to achieve the highest possible performance.
Compared to TCP/IP a young alternative is RDMA. It requires NICs that are RDMA capable. It can run over InfiniBand networks, which come with their own cables and switches. It can run over enhanced ethernet (DCB) or on top of TCP/IP via an iWARP NIC. It is all about enhancing performance while reducing load on the CPUs of your machines.
drbdmeta is used to prepare meta-data on block devices before they
can be used for DRBD. You can use it to dump and inspect this
meta-data as well. It is comparable to
drbdsetup is the low level tool that interacts with the DRBD kernel
driver. It manages the DRBD objects (resources, connections, devices, paths). It can modify all properties, and can dump the kernel driver's active configuration. It displays status and status updates.
drbdadm processes configuration declarative configuration files. Those files are identical on all nodes of an installation.
drbdadm extracts the necessary information for the host it is invoked on.
Enables OpenNebula users to base clouds on DRBD9/DRBD Manage
Status: Release Candidate 1
DRBD for MS Windows
Release planned with Version 9.0.2
PeerDirect allows a write request to be sent from an InfiniBand HCA directly to an NVMe device
Support Power8, enabling access to LINBIT's products
Released – with IBM in Germany – November 12
Enables OpenStack users to base their clouds on DRBD9/DRBD Manage
Released - Tokyo Open Stack Summit - October 16
Multi-path support: Aggregates bandwidth of configured paths; increases replication link availability
Release planned for November 2016