Design And Implement Of Synchronous Network Backup System Based On Linux

Data backup and disaster tolerance is very important for pivotal systems. After "9?11" accident, nearly 40% companies in the World Trade Center are close down, because the important data of these companies has lost. However, because of the lack of domestic disaster tolerance products and the expensiveness of the international products, many organizations such as government department, military units, companies and factories, have not disaster tolerance system. If disasters happen, the important information of these organizations will lose. The domestic research on backup technology is in the phase of beginning, and the government is improving the investment of the domain of data backup and disaster tolerance. As a result, the research of backup technology with independent property and production of relate products will have important political meaning and wide application.The current backup strategy could be classified in several aspects: complete backup and incremental backup; logical backup and physical backup; synchronous backup and asynchronous backup.A synchronous network backup system (SNB) is presented, and it implement synchronous backup in physical layer. SNB system is working at the interface of file system layer to device driver layer in Linux Kernel, so it is transparent to user. For each block that needs to be backup, SNB system transmit it to the remote backup server first, and then submit it to local disk device if the transmission is success. Therefore the procedure of backup is synchronous.Experimental results show that the efficiency of SNB system is satisfied when bandwidth is 100 Mbps. The storage spending of synchronous backup is little more than that of local storage. When storing files, user would not feel any difference between original system, and the data has already been backup to remote server.Specifically, the contribution of the paper includes:has discussed the current domestic and international backup methods.has analyzed Linux 2.4 Kernel. The procedure of Linux kernel storage could be divided into 3 parts: first, data is copied to the block buffers. Second, kernel thread bdflush submit the dirty blocks to disk device. Third, disk device will send an interrupt to kernel when write-procedure is finished.has presented the Synchronous Network Backup system (SNB), which implement synchronous backup in physical layer. By default, user process may return to user mode after the first procedure is finished, however, the second and third procedure will be finished asynchronously. The ext2 file system of Linux Kernel is modified also in the paper, that make process do not return immediately after first procedure, but go through with the second procedure to startup the transmission of block.SNB system is implemented based on Linux Kernel, and it is transparent to user.The modification in Linux Kernel wouldn't reduce the efficiency of the original function, especially the non-backup data.SNB system achieves high backup-efficiency and throughput.