1. Self Stabilizing Distributed File System Implementing a VFS Module

2. A File System Data storage Single server For example:For example: your home account!

3. Distributed File System Multiple servers - replicas Load balancing Fault Tolerance Problems:Problems: –Synchronization –Locking –From anyplace – see the same view

4. Self Stabilization A self-stabilizing system is a system that can automatically recover following the occurrence of (transient) faults. The idea is to design system that can be started in an arbitrary state and still converge to a desired behaviour.

5. Project ’ s Goal Create a Transparent Interface Between the User and the Distributed File System (SRFS)

6. The Linux File System Design The shell VFS layer EXT2SRFS Other F/S System calls User space Kernel space Programs

7. The VFS Provides the filesystem interface to userspace programs. It provides an abstraction layer (within the kernel) which allows different filesystem implementations to co-exist. VFS layer EXT2 interface SRFS interface Other F/S interfaces

8. User Space - Kernel Space Our file system is partitioned: –Caching daemon Networking Locking Synchronization and semantics –VFS module File access interface Manage the object store (see later) –Communication channel Using a character device

9. Our File System Design User space Kernel space The shellPrograms VFS layer System calls SRFS Object Store Character device Caching Daemon

10. Kernel Programming Writing in “C” only No standard libraries!!! Debugging is hard Use only kernel specific API Bugs: the system halts  reboot

11. FINI