中文摘要：

设计实现了一个基于I/O（输入输出端口）的广域网数据异步复制系统（DARS）,提出了一种基于＂活动日志＋位图＂的数据复制方法,以较小的空间和时间开销,解决了生产中心掉电或网络阻塞造成的生产中心与灾备中心数据不一致问题.采用独立缓存代理,实现了数据缓冲服务的灵活部署,确保了低带宽复制链路下系统的I/O吞吐率.系统实现和测试表明：与基于日志卷的数据异步复制系统LogDARS相比,DARS以33%的日志存储空间开销,获得了20%的写性能提高.

英文摘要：

An I/O-based data asynchronous replication system（DARS）over WAN（wide area network）was designed.A data synchronization method based on ＂active log＋bitmap＂was proposed to solve the data inconsistency problem caused by apower outage in the production center or network congestion,at the expense of a little time and size overhead.An independent caching proxy was adopted,which made it possible for data buffer to be deployed flexibly.In addition,it also guaranteed the system′s high I/O throughput over a low bandwidth network.The implementation and test indicate that compared with LogDARS,a log volume based data asynchronous replication system,the proposed system′s write performance increases by 20%,with a log storage space overhead of only33%.