Gluster provides Software Defined Storage for the cloud, and is gaining new functionality with every release.
The Gluster project tries to release a major version every few months. Each version introduces many new features. Recently added features include sub-directory mounts, improved volume state output, improvements to disperse volume performance and functionality, and many more.
Gluster is a scalable network filesystem. Using common off-the-shelf hardware, you can create large, distributed storage solutions for media streaming, data analysis, and other data- and bandwidth-intensive tasks. Gluster is free.