Distributed architectures support increased load on popular web sites by dispatching client requests transparently among multiple servers in a cluster. Packet Single-Rewriting technology and client address hashing alg...Distributed architectures support increased load on popular web sites by dispatching client requests transparently among multiple servers in a cluster. Packet Single-Rewriting technology and client address hashing algorithm in ONE-IP technology which can ensure application-session-keep have been analyzed, an improved request dispatching algorithm which is simple, effective and supports dynamic load balance has been proposed. In this algorithm, dispatcher evaluates which server node will process request by applying a hash function to the client IP address and comparing the result with its assigned identifier subset; it adjusts the size of the subset according to the performance and current load of each server, so as to utilize all servers' resource effectively. Simulation shows that the improved algorithm has better performance than the original one.展开更多
There are two kinds of dispatching policies in content-aware web server cluster; segregation dispatching policy and mixture dispatching policy. Traditional scheduling algorithms all adopt mixture dispatching policy. T...There are two kinds of dispatching policies in content-aware web server cluster; segregation dispatching policy and mixture dispatching policy. Traditional scheduling algorithms all adopt mixture dispatching policy. They do not consider that dynamic requests＇ serving has the tendency to slow down static requests＇ serving, and that different requests have different resource demands, so they can not use duster＇s resource reasonably and effectively. This paper uses stochastic reward net （SRN） to model and analyze the two dispatching policies, and uses stochastic Petri net package （SPNP） to simulate the models. The simulation results and practical tests both show that segregation dispatching policy is better than mixture dispatching policy. The principle of segregation dispatching policy can guide us to design efficient scheduling algorithm.展开更多
Software rejuvenation is a recently proposed practive fault-tolerance approach to counteract software-aging phenomenon. Compared with clusters of a flat architecture, all the nodes share the same functions. The applic...Software rejuvenation is a recently proposed practive fault-tolerance approach to counteract software-aging phenomenon. Compared with clusters of a flat architecture, all the nodes share the same functions. The application of software rejuvenation on dispatcher-based web server farms is discussed, which employ rejuvenation both on the dispatcher and the worker pool. Stochastic reward net (SRN)models for time-based and prediction-based rejuvenation policies are constructed respectively and solved by stochastic Petri net package (SPNP). Numerical results show that appropriate rejuvenation strategies on the dispatcher and the worker pool could significantly reduce the expected downtime cost of the whole web server farm.展开更多
针对传统露天矿生产管理模式下人工计数的弊端,以及当前部分专题数据库未能充分利用空间数据的现状,从GIS空间分析的角度出发,提出以SQL Server 2008作为后台数据库的露天矿卡车调度系统数据库构建方案。在分析卡车调度系统需求的基础上...针对传统露天矿生产管理模式下人工计数的弊端,以及当前部分专题数据库未能充分利用空间数据的现状,从GIS空间分析的角度出发,提出以SQL Server 2008作为后台数据库的露天矿卡车调度系统数据库构建方案。在分析卡车调度系统需求的基础上,完成了数据库的概念设计、逻辑设计、物理设计及实现。该方案利用SQL Server2008新增的Geography数据类型存储并处理空间数据,将矿区的基础空间数据及卡车运行轨迹作为分析依据,具备车辆位置显示、轨迹回溯、卡车工作量自动统计等功能,确保了工作量统计的准确性,节约了人工成本,为进一步推动露天矿生产管理的现代化提供了有力的技术支撑。展开更多
基金This work was supported by the National "863" program of China ( No.2003AA148010) and National Torch Project of China (No.2001EB001233) .
文摘Distributed architectures support increased load on popular web sites by dispatching client requests transparently among multiple servers in a cluster. Packet Single-Rewriting technology and client address hashing algorithm in ONE-IP technology which can ensure application-session-keep have been analyzed, an improved request dispatching algorithm which is simple, effective and supports dynamic load balance has been proposed. In this algorithm, dispatcher evaluates which server node will process request by applying a hash function to the client IP address and comparing the result with its assigned identifier subset; it adjusts the size of the subset according to the performance and current load of each server, so as to utilize all servers' resource effectively. Simulation shows that the improved algorithm has better performance than the original one.
基金Supported by the National Natural Science Foun-dation of China (90204008) the Science Council of Wuhan(20001001004)
文摘There are two kinds of dispatching policies in content-aware web server cluster; segregation dispatching policy and mixture dispatching policy. Traditional scheduling algorithms all adopt mixture dispatching policy. They do not consider that dynamic requests＇ serving has the tendency to slow down static requests＇ serving, and that different requests have different resource demands, so they can not use duster＇s resource reasonably and effectively. This paper uses stochastic reward net （SRN） to model and analyze the two dispatching policies, and uses stochastic Petri net package （SPNP） to simulate the models. The simulation results and practical tests both show that segregation dispatching policy is better than mixture dispatching policy. The principle of segregation dispatching policy can guide us to design efficient scheduling algorithm.
文摘Software rejuvenation is a recently proposed practive fault-tolerance approach to counteract software-aging phenomenon. Compared with clusters of a flat architecture, all the nodes share the same functions. The application of software rejuvenation on dispatcher-based web server farms is discussed, which employ rejuvenation both on the dispatcher and the worker pool. Stochastic reward net (SRN)models for time-based and prediction-based rejuvenation policies are constructed respectively and solved by stochastic Petri net package (SPNP). Numerical results show that appropriate rejuvenation strategies on the dispatcher and the worker pool could significantly reduce the expected downtime cost of the whole web server farm.
文摘针对传统露天矿生产管理模式下人工计数的弊端,以及当前部分专题数据库未能充分利用空间数据的现状,从GIS空间分析的角度出发,提出以SQL Server 2008作为后台数据库的露天矿卡车调度系统数据库构建方案。在分析卡车调度系统需求的基础上,完成了数据库的概念设计、逻辑设计、物理设计及实现。该方案利用SQL Server2008新增的Geography数据类型存储并处理空间数据,将矿区的基础空间数据及卡车运行轨迹作为分析依据,具备车辆位置显示、轨迹回溯、卡车工作量自动统计等功能,确保了工作量统计的准确性,节约了人工成本,为进一步推动露天矿生产管理的现代化提供了有力的技术支撑。
