In this paper, client-proxy-server based volume callback algorithms are introduced to address two key issues that face the traditional algorithms: scalability and client disconnection. Proxies extend scalability by alleviating loading on servers. Volume based callback accelerates validation process and eliminates revalidation bottleneck when reconnected. Simulation results show that the improved volume callback algorithms save validation messages by 86% compared with the traditional algorithms. And its overall performance is close to ATTL(adaptive time to live)algorithm.