Storage Area Network (SAN)

A storage area network (SAN) is a high-speed network that provides access to data storage at the block level. It connects servers with storage devices like disk arrays, RAID hardware, and tape libraries. In these configurations, the server’s operating system views the SAN devices as if they were directly connected. The data stored on those devices is then made available to all authorized users on the network, even if they’re in a different part of the data center or office building. 

As more storage devices are added to a SAN, they too will be accessible from any server in the larger network. A storage area network can be anything from two servers on a network accessing a central pool of storage devices to several thousand servers accessing many millions of megabytes of storage.

What do storage area networks do? 

SANs:

  • Make multiple storage devices available across a network, including different locations within a data center (depending on the length of the cables)
  • Reduce data silos, so data is not confined to one device or area
  • Reduce bandwidth bottlenecks that occur in LAN-based storage 
  • Allow serverless backup, in which storage devices directly copy data to a backup device across the network

A simple SAN consists of at least one SAN switch, storage device, and server, with cables to connect the various elements together and SAN management software. It also includes routers, bridges, and gateways to extend the SAN over large areas, including other parts of the data center network. The SAN’s topology depends on its size and the needs of the organization.

Deploying a SAN requires several steps. 

  1. The design of the SAN must take into account an organization’s current needs and future scalability requirements. 
  2. The vendor or vendors to provide the hardware, software, and any related services must meet the budget and reliability requirements. 
  3. The hardware and software must be installed and configured for managing the SAN. 
  4. The SAN is deployed, a complicated process that requires specialized knowledge and detailed planning, especially for a large network.

Storage area networks are most commonly implemented using a technology called Fibre Channel. Fibre Channel is a set of communication standards that supports very fast data rates. Devices on the network are normally connected together through a special kind of switch, called a Fibre Channel switch, that acts as a connectivity point for the devices. This provides a dedicated path between the devices in the SAN fabric, so they can use the entire bandwidth for the duration of the communication.

Several different industry groups have developed standards related to SAN technology. The most prominent is arguably the Storage Networking Industry Association (SNIA), which promotes the Storage Management Initiative Specification (SMI-S) and related standards. The Fibre Channel Industry Association (FCIA) also promotes standards related to SAN and administers the SANmark Qualified Program.

Benefits of storage area networks

SANs are particularly helpful in backup and disaster recovery settings. Within a SAN, data can be transferred from one storage device to another without interacting with a server. This speeds up the backup process and eliminates the need to use server CPU cycles for backup. 

SANs utilize high-speed Fibre Channel technology or other networking protocols that allow the networks to cover a larger geographic area. That makes it more feasible for companies to store their backup data in remote locations.

Utilizing a SAN can also simplify some management tasks, potentially allowing organizations to hire fewer IT workers or to free up some IT workers for other tasks. It’s also possible to boot servers from a SAN, reducing the time and hassle involved in replacing or servicing a server.

Organizations often choose to deploy a storage area network because it offers better flexibility, availability, and performance than direct-attached storage (DAS). A SAN removes storage from the servers and consolidates it in a place where it can be accessed by any application, so it tends to improve storage utilization. These 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, SANs often provide better performance than DAS. SANs also usually improve availability because they offer multiple connections to and from the data center’s servers. In addition, separating the storage from the servers frees up the computing resources on the servers for other tasks not related to storage.

Also read: Top SAN Storage Arrays

Alternatives to storage area networks

Before the advent of SANs, data centers generally used direct-attached storage solutions. Direct-attached storage is directly connected to the server, residing either on the server or in a standalone storage device that is not part of a separate storage networking environment. External storage devices plug directly into the server. 

Many smaller organizations continue to use DAS today because it offers lower upfront costs than deploying a SAN. However, for larger companies, the benefits of a SAN often outweigh the costs.

Most recently, however, the rise of cloud storage and hybrid cloud environments has transformed the traditional SAN implementation. Cloud storage offers greater flexibility using software-defined storage services, but that flexibility often comes with a high price tag. As such, hybrid cloud solutions serve as a balance between the comparatively low cost SAN environments and the high flexibility cloud environments.

SAN vs. NAS

SAN is sometimes confused with network-attached storage (NAS). The primary difference is that NAS refers to an individual storage device that uses an Ethernet connection and SAN is a complex network comprising multiple devices, including NAS and other types of storage. NAS devices are relatively user-friendly and are commonly used by individuals at home or by small businesses, whereas SANs require some advanced administration and are more practical for large enterprises. 

Another difference is that a NAS device provides file-level storage for end users, while SANs can only be used for block-level storage. Operating systems see a SAN as a disk, while they see a NAS device as a file server.

Read next: What is NAS? | Network Attached Storage

This article was updated December 2021 by Jenna Phipps.

Vangie Beal
Vangie Beal
Vangie Beal is a freelance business and technology writer covering Internet technologies and online business since the late '90s.

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