BlackBerry PlayBook OS provides a rich variety of filesystems. Like most service-providing processes in the OS, these filesystems execute outside the kernel; applications use them by communicating via messages generated by the shared-library implementation of the POSIX API.
Most of these filesystems are resource managers as described in this book. Each filesystem adopts a portion of the pathname space (called a mountpoint) and provides filesystem services through the standard POSIX API (open() , close() , read() , write() , lseek() , etc.). Filesystem resource managers take over a mountpoint and manage the directory structure below it. They also check the individual pathname components for permissions and for access authorizations.
This implementation means that:
- Filesystems may be started and stopped dynamically.
- Multiple filesystems may run concurrently.
- Applications are presented with a single unified pathname space and interface, regardless of the configuration and number of underlying filesystems.
- A filesystem running on one node is transparently accessible from any other node.