- Multithreaded NBD server written in C with good performance.
- Well-documented, simple plugin API with a stable ABI guarantee. Let’s you export “unconventional” block devices easily.
- Liberal license (BSD) allows nbdkit to be linked to proprietary libraries or included in proprietary code.
There are also a handful of servers specialized for particular disk sources. A good example of that is this OpenStack Swift server. But you shouldn’t have to write a whole new server just to export a new disk type.
nbdkit hopefully offers a unique contribution to this field because it’s a general server with a plugin architecture, offering a stable ABI and a liberal license so you can link it to proprietary code (say hello, VDDK).