Network block device
On some operating systems, a network block device is a device node whose content is provided by a remote machine. Typically, network block devices are used to access a storage device that does not physically reside in the local machine but on a remote one. As an example, a local machine can access a hard disk drive that is attached to another computer.
Technically, a network block device is realized by three components: the server part, the client part, and the network between them. On the client machine, where the device node is to work, a kernel driver/module controls the device. Whenever a program tries to access the device, the kernel driver forwards the request (if the client part is not fully implemented in the kernel it can be done with help of a userspace program) to the server machine, where the data physically resides. On the server machine, requests from the client are handled by a userspace program.
Network block device servers are typically implemented as a user space program running on a general purpose computer. All of the function specific to network block devices can reside in a user space process because the process communicates with the client via conventional sockets and accesses the storage via a conventional file system interface.
The network block device client module is available on some Unix-like operating systems, including Linux and Bitrig. Since the server is a userspace program, it can potentially run on every Unix-like platform; for example, NBD's server part has been ported to Solaris.
- iSCSI: The "target-utils" iscsi package on many GNU/Linux distributions. The tgtd can configure the backing storage of a LUN to be any block device (disk, partition, etc.). This has widest adoption amongst IP-based block device presentation protocols.
- Loop device: a similar mechanism, but uses a local file instead of a remote one
- DRBD: Distributed Replicated Block Device is a distributed storage system for the Linux platform
- ATA over Ethernet: send ATA commands over Ethernet
- "git.bitrig.org: NBD: Implement Network Block Device support.". May 20, 2015.
- Miroslav Kripac and Masaryk University Brno (December 10, 2002). "Implementing Oracle Real Application Clusters Using Network Block Device Technology". Retrieved May 22, 2013.
- "iSCSI Adoption Continues its Upward Path".
- NBD Mailing List
- Network Block Device on Sourceforge
- The Network Block Device, the Linux Journal
- ggate in FreeBSD handbook, FreeBSD GEOM Gate presentation
- Enhanced Network Block Device
- nbd-verify aims to be a test kit to verify the protocol implementation as well as a data handling tester of NBD servers
- BNBD is an alternative NBD server implementation
- Global Network Block Device (GNBD)
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