SAN (Storage Area Networks)

In an effort to improve business productivity, corporations are implementing web and Internet applications such as customer relationship management (CRM), enterprise resource planning (ERP), and e-mail. This move has resulted in the accumulation of large amounts of corporate data, and these voluminous stores of data are critical to a company’s operation.

Large amounts of data require large amounts of storage. Storage area networks (SANs) have emerged as the premiere technology for advanced storage requirements. SANs address an IT manager’s needs by providing a scalable, manageable, and efficient deployment of mission-critical data.

Aside from offering advanced technology for storage needs, SANs also reduce costs when deploying highly scalable storage versus traditional direct-attached storage (DAS). Hence, SAN reduces cost and offers new levels of performance and scalability previously unavailable. It’s a popular technology that is still being defined and explored.

SAN addresses the following issues currently experienced with DAS:

Difficulty of managing large, distributed islands of storage from multiple locations
Complexity of scheduled backups for multiple systems
Difficulty of preparing for unscheduled outages
Inability to share storage among multiple systems
Sheer expense of distributed disk farms

SAN addresses these issues by doing the following:

Reducing management costs through centralized control for monitoring, backup, replication, and provisioning.
Reducing subsystem costs through any-to-any connectivity between storage and servers. This setup allows networks to match servers with underutilized storage subsystems.
Reducing backup costs through the centralization and consolidation of backup functionality.
Offering highly available disk services by providing redundant, multiple paths between servers and storage devices. This provision allows for automated failover across all storage in an easily scalable manner.
Offering highly scalable and location-independent disaster recovery. You can replicate entire data centers to multiple locations, allowing quick and efficient switchover if the primary data center becomes unavailable. DAS networks are unable to provide this level of disaster recovery.

Traditional JBOD (just a bunch of disks) DAS networks are file-system�' and platform-dependant. The disks are associated with a single set of servers, and only the attached host can access them. Examples include small computer systems interface (SCSI), fiber channel, and enterprise system connection (ESCON). Redundant Array of Inexpensive Disks (RAID) addresses fault tolerance.

Because SAN removes the device, operating-system, and location dependencies of traditional DAS, new capabilities emerge. Storage expansion no longer has an impact on servers and vice versa. Bandwidth is available on demand, and load-balancing can occur across multiple active paths.

Network Attached Storage Versus Storage Area Networks

Network Attached Storage (NAS)
NAS uses specialized file servers to connect storage devices to a network. NAS is well suited for collecting, storing, retrieving, and sharing data over IP networks. NAS also supports multiple operating systems, file system, and protocols. NAS is optimized for file-based access to shared storage over an IP network.

Storage Area Network (SAN)
A SAN is an independent network designed specifically for connecting storage devices. SANs are optimized for the efficient collection, storage, and retrieval of raw block data. Most SANs use fiber-channel interconnections and require a media converter to connect to an IP network.