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SANs address several ongoing and emerging issues faced by Distributed Technologies, such as the need for:.
• Greater overall capacity and flexibility of a unified storage system. SANs can join together a vast amount of storage resources and make those resources available to an equally vast number of application servers. When storage devices are attached directly to servers, they cannot easily be shared. Adding capacity means taking applications out of service in order to reconfigure the server. For large data centers with over a hundred system and application servers, the cost of maintaining server-attached storage is high.
• Better utilization of storage. When storage is consolidated in a SAN, it can quickly and easily be reallocated. With server-attached storage, designers are forced to provision extra capacity at each server. On a day-to-day basis, this unutilized capacity is stranded. With a SAN, capacity allocation is enterprise wide. As a result, storage managers gain both a higher utilization of available storage and the ability to add storage resources as necessary. As an example, a typical server will be configured with a RAID Array of three 18 GB drives. With RAID 5, inherently one-third of all participating drives in this configuration are used for data striping. Additionally, only about forty percent of the available space is needed for servicing applications, thus "stranding" the remaining storage. In this scenario, only slightly over 25 percent of allocated storage space is actually utilized, with the rest dormant and unusable. In a dynamic SAN environment, space can be allocated when and where needed, making much more efficient use of aggregate data. .
• Highly available data in support of highly available applications. Within a SAN, data availability is dependent on the availability of its storage devices as well as its network components (e.
