Storage area network
[3]: 9 It grew out of data-centric mainframe architectures, where clients in a network can connect to several servers that store different types of data.
Transfer of data between storage devices, such as for backup, happens behind the servers and is meant to be transparent.
[3]: 22 In a NAS architecture data is transferred using the TCP and IP protocols over Ethernet.
Distinct protocols were developed for SANs, such as Fibre Channel, iSCSI, Infiniband.
Within the SAN, a range of data storage devices may be interconnected, such as SAN-capable disk arrays, JBODS and tape libraries.
Through the host adapters the operating system of the server can communicate with the storage devices in the SAN.
[4]: 26 In Fibre channel deployments, a cable connects to the host adapter through the gigabit interface converter (GBIC).
GBICs are also used on switches and storage devices within the SAN, and they convert digital bits into light impulses that can then be transmitted over the Fibre Channel cables.
Conversely, the GBIC converts incoming light impulses back into digital bits.
SAN switches connect the servers with the storage devices and are typically non-blocking allowing transmission of data across all attached wires at the same time.
It can include a variety of hard disk and magnetic tape devices that store data.
The LUNs allow for the storage capacity of a SAN to be segmented and for the implementation of access controls.
When a storage device receives a request to read or write data, it will check its access list to establish whether the node, identified by its LUN, is allowed to access the storage area, also identified by a LUN.
This software organizes the servers, storage devices, and the network so that data can be transferred and stored.
[2]: 176 In 1999 Common Information Model (CIM), an open standard, was introduced for managing storage devices and to provide interoperability, The web-based version of CIM is called Web-Based Enterprise Management (WBEM) and defines SAN storage device objects and process transactions.
As such, a SAN does not provide data file abstraction, only block-level storage and operations.
If multiple systems were simply to attempt to share a LUN, these would interfere with each other and quickly corrupt the data.
File systems have been developed to work with SAN software to provide file-level access.
Video editing systems require very high data transfer rates and very low latency.
SANs in media and entertainment are often referred to as serverless due to the nature of the configuration which places the video workflow (ingest, editing, playout) desktop clients directly on the SAN rather than attaching to servers.
Some factors that affect SAN QoS are: Alternatively, over-provisioning can be used to provide additional capacity to compensate for peak network traffic loads.
However, where network loads are not predictable, over-provisioning can eventually cause all bandwidth to be fully consumed and latency to increase significantly resulting in SAN performance degradation.
