What Is a SAN?

A Storage Area Network (SAN) is a specialized, high-speed network that provides block-level network access of storage to computers. SAN’s are typically made of hosts, switches, storage elements, and storage devices that are interconnected using a variety of technologies, topologies, and protocols. SANs may also span multiple sites which requires high speed point to point connection.

SANs are often used for

  • Improve application availability with no down time (ex:  Multiple Data Paths)
  • Enhance application performance with greater speed (ex: Off-Load Storage Functions, Segregate Networks )
  • Increase storage utilization and effectiveness (ex: consolidate storage resources, provide tiered storage, etc.) with improved data protection and security.

SANs always plays an important role in an organization’s Business Continuity Management (BCM) activities.

A SAN presents storage devices to a host such that the storage appears to be locally attached. This simplified presentation of storage to a host is accomplished through the use of different types of virtualization.

Figure 1-2

SANs are commonly based on Fibre Channel (FC) technology that utilizes the Fibre Channel Protocol (FCP) for open systems and proprietary variants for mainframes. In addition, the use of Fibre Channel over Ethernet (FCoE) makes it possible to move FC traffic across existing high speed Ethernet infrastructures and converge storage and IP protocols onto a single cable. Other technologies like Internet Small Computing System Interface (iSCSI), commonly used in small and medium sized organizations as a less expensive alternative to FC, and InfiniBand, commonly used in high performance computing environments, can also be used. In addition, it is possible to use gateways to move data between different SAN technologies.

SAN Performance Compared to DAS

Organizations often choose to deploy a storage area network because it offers better flexibility, availability and performance than direct-attached storage (DAS). Because a SAN removes storage from the servers and consolidates it in a place where it can be accessed by any application, it tends to improve storage utilization. Storage utilization improvements often allow organizations to defer purchases of additional storage hardware, which saves money and requires less space in the data center.

Thanks to high-speed connections (usually Fibre Channel), SANs often provide better performance than DAS. Also, because SANs usually offer multiple connections to and from the data center’s servers, they also improve availability. In addition, separating the storage from the servers frees up the computing resources on the servers for other tasks not related to storage.

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