For the 2.1 release notes including change logs, click here. Change logs are important because they spell out the Linux kernel and IB versions the release was built with, along with other important notes.
Whamcloud invests a huge amount of time and resources into ensuring that every release is high quality. However, Whamcloud recognizes that many Lustre users would rather run a release that is well-proven in production even if it means foregoing some of the newer features. To meet the needs of these customers, Whamcloud designates a certain release to be its maintenance release stream and produces regular bugfix only updates for this release stream. These releases are what the majority of Whamcloud's customers choose to run in production.
Feature Releases and Roadmap
Whamcloud is continually developing new features required by future versions of Lustre. Users who want to use these capabilities can access them first in feature releases. Feature releases will also contain all the latest bugfixes from previous releases. Periodically a new feature release will be designated the new maintenance release stream.
For the current plans for both maintenance and feature releases, please see the Lustre Roadmap