The Design And Implementation Of A Continuous Data Protection System Server

Nowadays, data is essential to enterprises. It is very important to quickly and correctly recover data in the case of an error or disaster. Many analysis show that traditional data protection technologies work well on hardware failure and natural disasters but have a limitation on human caused errors. They can not provide the ability to keep data change and restore data at any point of time. As a result, a new Continuous Data Protection (CDP) technology comes out. This paper focuses on Continuous Data Protection solutions in Local Area Network, designs and implements a file-level CDP Server and the main framework of a block-level CDP Server.The file-level CDP System works above file system. It captures real-time changes of single file and provides the ability to recover data at any point of time. The system utilizes a delta algorithm to compute the differences between two versions of file in order to make a bandwidth-efficient transition. Different versions of file are kept at server with carefuly designed integration of mirroring and incrementing. All commands are divided into two catalogs, synchronized and synchronized, according to estimated execution time. All synchronized commands are executed immediately while all synchronized commands are inserted into a queue, waiting for execution by a multi-threaded worker. This design guaranties a short response time on small tasks and better performance on heavy work load. Also, this paper presents an index structure to find out all the versions that contains certain files by file name. What's more, the system performance on single task and multi-tasks is analyzed.The block-level CDP System works on raw disk. It captures all write command to disk by OS driver. The data is transmitted via iSCSI protocol which directly maps protection space at server to the protected computer locally. Each disk protection is mapped into two individual LUN with same data at different version. In this way, history data can be viewed while not interrupting normal data protection. The state and work flow design of server allows user to temporarily replace the original protected disk with CDP virtual disk when performing data restoring, which provides rapid resumption of business.