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.
Benefits of SAN
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. Also, many 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 hassles 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.
Alternatives to SAN
Before the advent of SANs, data centers generally used direct-attached storage (DAS) solutions. As the name implies, direct-attached storage is directly attached to the server, residing either on the server or in a standalone storage device that is not part of a separate storage networking environment. 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 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 comprised of 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 distinction 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.
How SAN works
A simple SAN consists of the following components:
- a SAN switch
- a storage device
- a server
- cables to connect the various elements together
- SAN management software
In most real-world settings, a SAN will include many different switches, storage devices, and servers. It will also likely include routers, bridges, and gateways to extend the SAN over large areas and connect to other parts of the data center network. The SAN’s topology will depend on its size and the needs of the organization.
The process of deploying a SAN requires several steps. First, the design of the SAN must take into account an organization’s current needs and future scalability requirements. Second, the vendor or vendors to provide the hardware, software, and any related services must meet the budget and reliability requirements. Next, the hardware and software must be installed and configured for managing the SAN. The final and most complicated step is actually deploying the SAN a process that requires specialized knowledge and detailed planning, especially for a large SAN.
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.