DNBD (Distributed Network Block Device) is a read-only and caching network block device specially developed with stateless/diskless Linux client operation in mind. See more on stateless Linux at OpenSLX
DNBD supports following main features:
- Replication of servers for robustness
- Multicast communication and caching of network traffic for scalability
These characteristics make it suitable especially for use in wireless networks, e.g. for diskless/stateless clients or to share multimedia files in such an environment. The servers can export a file or block device equipped with a operating system, movies, music, etc. Several clients can import the block device and access it like a local hard disk. However, each block transfer over the network can be cached by all clients: If several users on each client start to watch a movie within a certain time interval, the movie data has to be transmitted only once (depending on the cache size). The network is not burdened with unnecessary traffic.
DNBD can be used together with cowloop, UnionFS or AUFS in order to get local write semantics, e.g. for diskless clients. Especially in wireless environments with limited bandwidth, caching can increase boot-up time enormously.