NBD (Network Block Device)
The NBD protocol allows a block device (or a file containing an image of a block device) to be exported from one machine to another. Typically it would then be mounted as a filesystem or used as a swap area. Exported devices are identified by the IP address and TCP port number from which they are hosted.
NBD differs from NFS in that the filesystem on the block device is interpreted by the client as opposed to the server. This has the advantage that the filesystem will behave more like one on a locally-attached disc, but the disadvantage that (except in special cases) only one client can use the device at any given time.
Common uses of NBD include:
- the provision of storage to discless machines, and
- accessing a removable storage device from one machine when it is physically attached to another machine.