A storage area network (SAN) is a network which provides access to consolidated, block level data storage.

About SAN

SANs are used to enhance storage devices, such as disk arrays, tape libraries, and optical jukeboxes, accessible to servers.

A SAN has its own network of storage devices that are generally not accessible through the local area network (LAN) by other devices.

The cost and complexity of SANs dropped in the early 2000s to levels allowing wider adoption.

A SAN does not provide file abstraction, only block-level operations.

However, file systems built on top of SANs do provide file-level access, and are known as shared-disk file systems.

Types of SAN

1. Virtual SAN
A virtual storage-area network (VSAN) is a software-defined storage offering on top of a hypervisor such as VMware ESXi or Microsoft Hyper-V.

2. Unified SAN
Unified SAN is based around the concept of unified storage, which exposes file storage and block storage through a single device (usually a modified NAS appliance).

3. Converged SAN
Storage-area networks are normally kept separate from Ethernet networks.

SAN pros and cons

The main benefit SAN is that raw storage is treated as a pool of resources.

SANs are also highly scalable because additional capacity can be added as required.

The main disadvantages to SANs are cost and complexity.

SAN hardware tends to be expensive, and building and managing a SAN requires a specialized skill set.

SAN vs. NAS

The terms SAN and NAS are sometimes confused with one another because the acronyms are so similar.

NAS consists of a storage appliance that is plugged directly into a network switch. Although there are exceptions, NAS appliances are often used as file servers.