Network-Attached Storage

Network-attached storage, or NAS, is a file service reached over a network. The server owns the file system and exposes a share or export. Clients see files and directories through a protocol such as SMB or NFS instead of receiving a raw block device.

A client application calls its local file interface. The SMB or NFS client translates that operation into protocol requests and sends them across the network. The NAS server authenticates the client, maps its identity, applies share and file permissions, coordinates protocol state, accesses its file system, and reaches backing storage. DNS, directory services, time, network paths, server state, and storage all become dependencies.

NAS differs from SAN and direct-attached storage

NAS exports a file namespace, so the server controls file-system consistency. A SAN exports block storage, so the host normally controls the file system. Direct-attached storage connects devices to one host. These models can use similar disks and networks, but they divide ownership and failure handling differently.