Storage Area Network (SAN)
Definition
A Storage Area Network (SAN) is a high-speed special-purpose network (or sub network) that interconnects different kinds of data storage devices with associated data servers on behalf of a larger network of users. Typically, a SAN is part of the overall network of IT resources for an enterprise. A SAN is usually clustered in close proximity to other IT resources but may also extend to remote locations for backup/recovery and archiving storage.
SAN is a specialized, high-speed network attaching servers and storage devices and, for this reason, it is sometimes referred to as “the network behind the servers”. A SAN allows any-to-any connection across the network, using interconnects elements such as routers, gateways, hubs, switches and directors. It eliminates both the traditional dedicated connection between a server and storage, and the concept that the server effectively “owns and manages” the storage devices. It also eliminates any restriction to the amount of data that a server can access, currently limited by the number of storage devices attached to the individual server. Instead, a SAN introduces the flexibility of networking to enable one server or many heterogeneous servers to share a common storage utility, which may comprise many storage devices. Additionally, for higher security, the storage utility may be located far from the servers.
Why?
Traditional means for connecting servers and storage can no longer satisfy today's requirements for fast access to massive amounts of data. SCSI technology uses parallel cabling which severely limits speed, distance and the number of attached storage devices. Configuring SCSI (Small Computer Systems Interface) connections to support terabytes of data is impractical. In addition, traditional server/storage connections make the server the exclusive owner of its attached storage. As computing environments move from a server centric to data centric model, access to shared data resources becomes critical. Storage Area Networks are an enabling technology that allows storage resources to be shared in order to provide continuous, faster and easier access to data.
A SAN consists of a communication infrastructure, which provides physical connections; and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust.
The primary benefits of a SAN are:
- Availability: A single copy of data is accessible to any and all servers via multiple paths
- Reliability: Dependable data transportation ensures a low error rate, and an ability to recover from failures is provided
- Scalability: Servers and storage devices may be added independently of one another, and do not depend on proprietary systems
- Performance: Fibre Channel (the standard method for SAN interconnectivity) has high bandwidth and low overhead, and it separates storage and network I/O
- Manageability: Emerging software and standards for different fibre channel topologies which allow single centralized management and proactive error detection and correction
- Return On Information Management: Due to increased redundancy and superior manageability, as well as the ability to add storage and servers independently of one another, SAN’s provide a lower cost of ownership and a higher return on information management