中文摘要：

为提高软件即服务（SaaS）应用中资源的访问效率,提出支持SaaS服务重要特征的负载均衡策略。首先,结合SaaS服务的多租户和高度可伸缩两大特性,提出一种基于租户请求分流、在局部和全局两个层次伸缩的负载均衡策略;其次,对所提出负载均衡策略用Petri网进行建模并仿真;最后,将提出的负载均衡策略与轮询（RR）、随机和改进的最小连接（ILCS）负载均衡算法在总体响应时间和总吞吐量两方面进行比较。实验结果表明：在请求速率达到500请求/秒后,所提策略的总体响应时间和总吞吐量趋于稳定并优于另外三种算法。

英文摘要：

To improve the efficiency of resource access in Software as a Service （SaaS） applications, a load balancing strategy combined with the important features of SaaS service was proposed. Firstly, the load balancing strategy was proposed by combining multi-tenancy and high scalability in SaaS service based on the distribution of request and global and local scalability. Secondly, the load balancing strategy model was constructed and simulated by a Petri net. Finally, this strategy was compared with Round Robin （RR）, stochastic algorithm and Improved Least-Connection Scheduling （ILCS） load balancing algorithm in response time and throughput. The experimental results show that the response time and throughput of the proposed strategy become stable and they are superior to the other three algorithms after the request rate reaches 500 per second,