The Caveats for SAN

The caveats for SAN are several. The main issues of complexity and cost center around the heterogeneous nature of the SAN itself. Because SANs are configured with several discrete components (see Figure 4-5), the complexity of configuration and implementation becomes a challenge.

Cost becomes an issue as the SAN devices remain fairly new to storage infrastructure markets and therefore have not reached commodity-pricing status. Its also important to note the rapid change due to the relative immaturity of the products, and the reliance on other areas of technologies such as Operating Systems, storage devices, and management software. The associated cost in terms of user knowledge and training in new technologies that make up the SANsuch as switches, fabrics , Fibre Channel, and HBAscontribute to this caveat.

However, an often-overlooked challenge is the esoteric nature of the logical extensions of a servers software that deals with storage. File systems, volume managers, and physical I/O operations all play necessary roles in performing storage operations. Within the SAN, these operations become more logical and have to coexist with other servers that share the fabric network and devices connected. I/O functions must extend into the fabric itself and operate through Fibre Channel software, storage software, and device micro-code, all being remote to the server. These new software functions encapsulated within the FC fabric (some of them user accessible and some micro-code enabled) drive the next logical caveat: management.

Management of the SAN remains problematic even though new products and solutions continue to appear. However, this scenario of rapid change, due to the newness of the technology, largely renders only management solutions, which in the end will be merely transient given that SANs will continue to outgrow their simple configurations, add significant new functions from software vendors , and become integrated with other network and server technologies.

On the other hand, SANs provides the next generation of scalable solutions for large-scale enterprise applications. The SAN architecture supports environments that require scalable solutions for large user populations that access datacentric (that is, database-driven) information that has read/write volatility. This has proven itself within the enterprise data centers where SANs are the solution of choice given their capability to handle large amounts of data, using applications such as OLTP and Data Warehousing. In addition, customers who are dealing with large volumes of unstructured data (such as audio, video, and static images) are migrating to SANs to support these applications.

In discussing both the NAS and SAN architectures in summary fashion, a more thorough picture of the components that make them up will come to light. How these technologies operate, as well as how to apply their value to solutions within data center settings, will be discussed in greater detail in Parts V and VI.