ing units (NPUs) are supposed to do most of the time- while it churns data at wire speed, it should also perform deep packet inspection and classification/for- warding. At the same time, however, an SNP operates in the heart of a SAN instead of an ordinary high-speed switch or router. As a result, the SNP must meet some peculiar and stringent functional and performance requirements that are beyond the capability of a typical NPU. The data storage area is extremely broad. It covers a very wide array of technologies from mag- netic materials and laser optics all the way to fiber-optic transmissions and fast electronics, and from unbelievable aerodynamic designs of read/write heads over fast rotating disks to sophisticated Downloaded from Digital Engineering Library McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. STORAGE NETWORK PROCESSORS (SNPS) STORAGE NETWORK PROCESSORS (SNPs) 195 Fibre Channel Fibre Channel loop switch FC-SCSI bridge Server Server SCSI RAID Traditional LAN FIGURE 11.1 The principle of a SAN. input/output (I/O) protocols and data management software. It is SO technologically rich that we can- not discuss it in this chapter. We will start our discussion by briefly mentioning fundamental concepts and technologies, but we will return quickly to the main thrust of the chapter-the SNP, why it is needed in the first place, and how it is different from other network processors. We will also provide some representative examples from industry leaders. Interested readers can obtain more information about these technologies in the sources listed at the end of this chapter. SAN-ENABLING TECHNOLOGIES For many reasons, Fibre Channel has been the de facto standard in SANs. At the same time, however, IT departments of large companies and organizations have undergone a revolution. The industry has identified the use of SAN technology as a key factor for the advancement of storage techno