基于主从异步复制技术的容灾实时系统研究与实现

介绍了一个实用的容灾实时系统SDP_R．为提高系统的性能，SDP_R采用严格的主从异步复制技术和多线程技术．实验表明，多线程技术和多进程技术能够较大地提高系统的性能，而且相比多进程技术，多线程技术所需的内存要少得多．详细探讨了采用多线程技术时怎样保证数据的一致性．SDP_R系统不仅满足容灾系统设计准则，而且与Oracle以及Informix等数据库提供商提供的数据复制技术相比，SDP_R通过数据库底层函数层可以屏蔽不同数据库产品或版本之间的差异，从而实现不同数据库产品和版本之间的数据复制．SDP_R适用于使用多种数据库产品或版本的系统，如智能网系统．同时，SDP_R系统可以处理数据拷贝图为任意拓扑结构的情况．容灾系统SDP_R已经实现，它是下一代智能网分布式SDP中的一个主要功能模块．

A Primary-Backup Lazy Replication System for Disaster Tolerance

Data is replicated in distributed systems to improve availability and performance Although replication is an intuitive, readily understood idea, its implementation is difficult In this paper, the design criterions of replication based distributed systems for disaster tolerance are presented, emphasizing that data replication should not disturb client applications that use the original database, and severe performance penalties associated with replication should be avoided A survey of current replication techniques is also presented Academically, the replication technique seems to be matured, but academic researches have little influence on the replication scheme used in commercial systems for the simple reason that they are complex and inefficient A simple and efficient real time system for disaster tolerance is introduced in this paper The system is based on the strict primary lazy update techniques Experiments show that multithreading technique and multiprocessing technique can improve performance, and multithreading technique consumes little memory So multithreading is used in this system But multithreaded servers typically lead to nondeterminism Its influence on replication is discussed in detail An evaluation of this system is also discussed, which proves that the system fulfills the design criteria proposed Compared to the replication techniques provided by database vendors such as Oracle and Informix etc, SDP R has sound advantages Its database interface layer hides the difference of database So it is suited for systems whose databases are provided by different database vendors Moreover, SDP R can guarantee serializability for arbitrary copy graphs The proposed system will be built within the architecture of the next generation of intelligent networks