Research And Implementation Of ISCSI Protocol

With the rapid development of network services represented by electronic commerce, the demands of information keep on increasing explosively. It makes the high-speed access of network data most important, as well as how to share in it. As a result of that, it becomes the key problem to build up information superhighway. As a new technology of network storage, iSCSI gets a special tow-ply character of network and I/O by integrating storage I/O with IP network. In setting up a heterogeneous storage network, iSCSI has an excellent merit incomparably to other protocols.Compared with other network storage technologies, such as Fabric Channel etc, iSCSI shows lower efficiency and higher utilizing rate of CPU. In addition, the implementations of iSCSI protocol fall short of reusability and portability, because it always has a tight association with actual applications.Firstly, this paper studies the architecture of iSCSI network storage. We analyses iSCSI at length from several facts, such as session management, naming and discovery, PDU, error recovery. For the low efficiency of iSCSI CRC algorithm, we decompose the digest information polynomial to replace original serial CRC by parallel CRC algorithm, by using the theory of Galoias domain. According to the characters of iSCSI PDU, we improve the implementation of parallel CRC algorithm in order to get a new fast parallel CRC checkout algorithm of iSCSI, so as to decrease the utilizing rate of CPU.Based on all above analysis and improvements, this paper designs and implements a prototype of the iSCSI protocol, which runs in Linux's kernel space. By means of hierarchal module structure, it assures the least independent to physical devices. It is a most abstract implementation of iSCSI, which has the characters of distinct structure, lower recourse occupation and preferable portability.At last, we test three performance measures, i.e. the throughout, the utilizing rate of CPU and delay, by taking IOMeter as the testing platform. The testing results show that the performance of iSCSI will be better than that of samba and nfs, when writing data or reading data whose size are no larger than 8K, and applying the improved CRC could decrease the utilizing rate of CPU.