This paper studies the important fault management issue with focus on the fast restoration mechanisms for Optical Burst Switched (OBS) networks. In order to reduce the burst losses during the restoration process, effective fast restoration schemes are necessary. This is illustrated via two basic fast restoration schemes, the distributed deflection scheme and the local deflection scheme, compared with the slow global routing update mechanism. A novel priority-based QoS restoration scheme is also proposed to provide differentiated restoration services. Through detailed descriptive analysis and a comprehensive simulation study, these fast restoration schemes demonstrate fast restoration process, low fault management overheads, and excellent burst loss performance. As far as we know, this is the first comprehensive study on the restoration mechanisms for OBS networks.