What is a network block device?

Network block device (NBD) is a remote data storage technique used in Linux® and UNIX® computer systems, which allows the client computer to access data storage on a remote system. Once the client computer sets NBD, it is used as if it was a disk on the client, unlike somewhere else on the network. The network block device on the server can be a real hard disk or even a special type of file that can be accessed as if it was a disk. Although slower than the local hard disk, the method is useful for a number of cases such as backup or compact computers without disk disk.

The use of a network block device in most cases means server and client model. What is referred to as a device node is maintained on the server. This is usually either a hard disk, a range of disks, or a file type often referred to as a disk on a disk. The server operates a small software called a demon that allows the client to access the device from the server and mount it onlocally. From the point of view of the client computer, access to the device node is as if it were another disk drive.

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network block device is in many ways similar to other UNIX® techniques known as the NFS system (NFS). However, one of the primary differences is the protocol through which communication occurs. NFS uses user datagram (UDP), while NBD uses TCP (TCP) protocol. Since UDP is something like a fire method and forgotten the transfer of packets in the network, it is sometimes prevented by the fact that the client must apply for repeated data transfers. TCP communication, on the other hand, follows the reserved connection between the client and the server and ensures that the NBD data is read and written from exactly.

This ability to implement a network block device allows SOME special types of disk mirroring to be created between the client and the server. This technique knows themIt has an unnecessary number of independent disks (RAID). With the RAID type settings, the data on one disk mirror on any number of other discs, which provides an instantly accessible backup if any of the discs failed. The box is basically perceived by the computer operating system as the only disk.

One such product that extensively uses the network block equipment is called a distributed replicated block device (DRBD®). DRBD® settings are often used for very large disk fields that require high availability. In this case, however, one disk field is set in RAID format and then reflects on other disk fields using NDB. DRBD® is then accessible to any number of client computers.