San Environment, High Availability File System Backup Program Realization

The SAN (Storage Area Network) makes it true that storage resources can be separated from servers, and can provide high performance data pipe with 100 MB/s and shared storage devices managed concentrically. This makes data access, backup and restore will not reduce performance of network largely. The targets or the advantages of storage based on SAN are to make access to vast data high availability, high security and high performance. At the same time, these three aims should be required in the design of the software for storage control and management based on SAN.The software for storage control and management based on SAN should take the advantages of SAN to offer the service of storage to users. But how the software to do these is one of the hottest researches recently. As far as recent backup system softwares are concerned, they only implement simple backup from one disk to other disk, but availability of access to the filesystems on the disk during backup and necessary system fault disposal are not taken into account. These above result in the low availability of these backup systems and cause the systems are hard to use by user. Even to some backup system, before backup is executed, the access service of filesystems must be stopped manully.This paper provides the solutions of filesystem backup based on SAN with high-availability. These solutions are designed aiming to acquire high-availability and slove to the problems of recent backup systems. The outstanding characters of the solutions are listed below:1. Replicate and Snapshot, the two types of backup are offered and user can choose the backup ways according to the different backup applications.2. Solve the problem of synchronous control between server's file system backup and data access to files and ensure that in the course of file system backup, file system access service is not ceased. The means our backup solutions get higher lever from disk lever to filesystem lever and they have qualities of high-availability.3. Foundmentally, the system fault disposals are taken into consideration in our solutions. Especially, disposals of path fault have been designed.4. Our solutions ensure that when backup is finished, the backup data and filesystems are immediately available and this point demonstrates furtherly high availability our solutions are.Based on the solutions that we have designed, we have developed one filesystem backup system, FSBackup. The system architecture and core data structure of FSBackup are described in this paper and more detail information of implementation of high availability solutions is also provided.