A server system including a first server to execute first role, other server to execute at other role, spare server and management layer server. The management layer server is configured to allocate first group of users to access first server and other group of users to access other server, receive status information sent by first server and status information sent by other server, analyse status information to determine an operational status of first server and operational status of other server, update role of spare server to first role when operational status of first server indicates failed state and reallocate first group of users to the spare server, and update a role of another spare server to the other role when the operational status of the other server indicates a failed state and reallocate the other group of users to the other spare server.