In contrast to a NAS, a SAN is a network of interconnected storage devices. It is a dedicated high-performance network for consolidated block-level storage. A SAN storage constitutes part of a Storage Area Network which provides storage facilities for the SAN Network. While both NAS and SAN provide network storage options, the difference lies in the way data are accessed.
The key difference here is, a NAS is connected to a client as a file server. The data on a NAS is managed by the NAS itself and thus presented as “files,”. But a SAN provides Block-level access to the clients, where the storage is presented to a client as a disk, visible in disk and volume management utilities. The client connects to the SAN as virtual local storage which can be formatted with a file system and mounted. The data on a SAN is managed by the client itself and not by the SAN Storage. SANs mostly use other network protocols like Fibre Channel and iSCSI instead of TCP/IP in NAS.
A SAN storage is designed specifically to handle structured workloads such as databases. Storage area networks are frequently deployed in support of business-critical, performance-sensitive applications such as Oracle databases, Microsoft SQL Server databases, Large virtualization deployments using VMware, KVM, or Microsoft Hyper-V, Large virtual desktop infrastructures (VDIs), SAP, or other large ERP or CRM environments, etc.