SNIA Definitions - Storage Networking Industry Association on storage area networks - Technology Information

Computer Technology Review, Sept, 1999

In any branch of technology, communication is facilitated if key terms are understood and used consistently among vendors and end-users. The following definitions of key storage-networking-related terms were created by the SNIA as a first step toward the association's concerted efforts to create a common language in the storage networking industry:

Storage Networking

Storage Networking is the practice of creating, installing, administering, or using networks whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements.

Storage Area Network (SAN)

A Storage Area Network (SAN) is a network whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements. 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.

Note: The SNIA definition specifically does not identify the term SAN with Fibre Channel technology. When the term SAN is used in connection with Fibre Channel technology, use of a qualified phrase such as "Fibre Channel SAN" is encouraged. According to this definition an Ethernet-based network whose primary purpose is to provide access to storage elements would be considered a SAN. SANs are sometimes also used for system interconnection in clusters.

SANs may enable:

* Sharing of heterogeneous storage resources among heterogeneous systems

* Consolidation of storage resources

* Separation of storage traffic from application traffic

* Independent scaling of computing and storage resources

* Centralized management of distributed storage resources

* Fault-tolerant data access

SAN-Attached Storage (SAS)

SAN-Attached Storage (SAS) refers to storage elements that connect directly to a SAN and provide file, database, block, or other types of data access services to computer systems.

Note: SAS elements that provide file access services are commonly called Network Attached Storage, or NAS devices.

Network-Attached Storage (NAS)

Network-Attached Storage (NAS) refers to storage elements that connect to a network and provide file access services to computer systems. A NAS Storage Element consists of an engine, which implements the file services, and one or more devices, on which data is stored.

Note: NAS elements may be attached to any type of network. When attached to SANs, NAS elements may be considered to be members of the SAS class of storage elements.

Characteristics of SAS and NAS may include:

* Simplicity of installation, use and maintenance

* Independent scaling of computing and storage resources

* Sharing of storage resources among heterogeneous computer systems

* Provision of shared data access to heterogeneous computer systems

* High data availability

Storage Element

In the context of these definitions, a Storage Element is any device designed and built primarily for the purpose of persistent data storage and delivery. This definition is specifically intended to encompass disk drives, tape drives, RAID array subsystems, robotic tape libraries, filers, file servers, and any other types of storage devices.