Design And Implementation Of Pionts Snapshot At Block Device Layer

Snapshot technology is the hot-line data backup an important means. Snapshot technology can be used effectively to avoid user errors, virus attacks, and other non-hardware failure caused the loss of data. A snapshot of existing technology and a number of issues: split mirror the lack of timeliness and require large amounts of storage space when writing copy and redirect most of the writing of the document to achieve, can only be for a particular file system, Backup windows and the need to back up directly proportional to the number of documents, in a backup in the process of spending more, the narrower scope of application.According to block device level a snapshot of the operation of equipment directly, I/O efficiency advantages, designed and implemented based on copy-on-write and redirect-on-write technology at block device-level multi-point in time snapshot. With a separate disk as a snapshot of the source data was kept updated version of the data set, and detailed design of the data storage; hash algorithm used for rapid snapshot of the meta-data, speed up the query speed memory only save Snapshot of the latest version of the meta-data, and the remaining snapshot of metadata stored in the disk, reducing the memory consumption; join the block version information form, can quickly find the source data after data blocks corresponding version of the latest snapshot, not for search Various versions of the source data for improved performance.Through a large number of experiments it shows that the design and realization of the snapshot with high performance. When copy-on-write to read and write performance and the general-readwrite of the disk to read and write a difference of around 20 percent, to redirect-on-write snapshot and the general-readwrite of the disk to read and write almost the same. At the same time when the copy-on-write of the reading performance is superior to redirect-on-write, and write in the poor performance to some, users can process data in accordance with their own characteristics, the system provides a flexible choice of two programmes snapshot.