You are a network administrator for your company. The company has a main office and two branch offices. The branch offices are connected to the main office by T1 lines. The network consists of three Active Directory sites， one for each office. All client computers run either Windows 2000 Professional or Windows XP Professional. Each office has a small data center that contains domain controllers， WINS， DNS， and DHCP servers， all running Windows Server 2003.   Users in all offices connect to a file server in the main office to retrieve critical files. The network team reports that the WAN connections are severely congested during peak business hours. Users report poor file server performance during peak business hours. The design team is concerned that the file server is a single point of failure. The design team requests a plan to alleviate the WAN congestion during business hours and to provide high availability for the file server.   You need to provide a solution that improves file server performance during peak hours and that provides high availability for file services. You need to minimize bandwidth utilization.   What should you do？ （）