Why Connect Storage to a Network?
Throughout the journey into storage networking, it's important to keep sight of the benefits being sought. Throughout this book we try hard to distinguish between the features of storage networking, such as universal connectivity, high availability, high performance, and advanced function, and the benefits of storage networking that support larger organizational goals, such as reduced cost and improved quality of service.
The specific benefits that storage networking delivers are different in every situation, but with storage networking, as with any other aspect of information technology, benefits can be broadly classified as either:
- Reducing the cost of providing today's information services or providing or enabling new services that contribute positively to overall enterprise goals.
Storage networking offers ample opportunity for an information services department to deliver both types of benefits. For example, in the realm of cost savings:
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If all online storage is accessible by all computers, then no extra temporary storage is required to stage data that is produced by one computer and used by others. This can represent a substantial capital cost saving.
- Similarly, if tape drives and robotic media handlers can be accessed directly by all computers, fewer of these expensive and infrequently used devices are needed throughout the enterprise. This, too, reduces total enterprise capital cost for information processing without diminishing the quality of service delivered.
- Probably most important, however, are the administrative and operational savings in not having to implement and manage procedures for copying data from place to place. This can greatly reduce the cost of people—the one component cost of providing information services that doesn't go down every year!
Similarly, consolidating storage on a network may enable information services departments to provide services that just aren't possible with storage attached directly to each computer. For example:
- SAN connectivity enables the grouping of computers into cooperative clusters that can recover quickly from equipment or application failures and allow data processing to continue 24 hours a day, every day of the year.
- With long-distance storage networking, 24 × 7 access to important data can be extended across metropolitan areas and indeed, with some implementations, around the world. Not only does this help protect access to information against disasters; it can also keep primary data close to where it's used on a round-the-clock basis.
- SANs remove high-intensity I/O traffic from the LAN used to service clients. This can sharply reduce the occurrence of unpredictable, long application response times, enabling new applications to be implemented or allowing existing distributed applications to evolve in ways that would not be possible if the LAN were also carting I/O traffic.
- A dedicated backup server on a SAN can make more frequent backups possible because it reduces the impact of backup on application servers to almost nothing. More frequent backups means more up-to-date restores that require less time to execute.
Figure 1.3 illustrates the role a SAN occupies in a distributed client/server computing network.
Figure 1.3 A SAN separates client traffic from disk I/O
