Research And Implementation Of The Snapshot Technology

As organizations and businesses depend more and more on digital information, Storage Vendors always focus on the data reliability because of the importance of data as the largest business assets of the companies. It is not the best data protection strategy that all of users in company adopt the same data protection strategy. Actually, not all of the users need this strategy to protect the data. The project proposed a user-based snapshot technology. It is the main idea that the different levels of data protection strategy will be adopted, according to the priority level of the user.The snapshot system was designed and implemented, which is used to hot backup on line. The theory of incremental back is implemented. The current snapshot version depends on the previous snapshot version. If the data isn't modified, the data is shared between them. The incremental bitmap is used to record the data which is modified after the previous snapshot version. The redirect-on-write method reduces the load of IO, comparing with copy-on-write. Snapshot using the hash table maintain the data mapping model, in order to redirect the request in constant time. According to user priority, snapshot generation time interval and the snapshot volume capacity are determined, during the user-based snapshot system.The function tests and performance tests run on the snapshot system, which is implemented in the project. The function of creating snapshot, recovering snapshot version and deleting snapshot version. The result of function test proved that it spent tens of microseconds on creating the snapshot version.The result of performance test on the system proved that the performance of read-write on the system with snapshot is worse than the performance of the read-write on the system without snapshot. If the size of IO block is larger than the size of the snapshot block, the respond time of the system is larger than the system, in which the size of IO block is smaller than the size of the snapshot block. The read-write rate and the random-sequence rate have impact on the performance of the system.