The Differences Between SAN and NAS

An Explanation of Storage Area Networks and Network Attached Storage

Businessman using computer in virtual server room
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Storage Area Networks (SANs) and Network Attached Storage (NAS) both provide networked storage solutions. A NAS is a single storage device that operates on data files, while a SAN is a local network of multiple devices that operate on disk blocks.

The differences between NAS and SAN can be seen when comparing their cabling and how they're connected to the system, as well as how communication to the device is performed.

Note: SAN is sometimes referred to as storage area networking but it means the same thing. It also stands for small area network and service agreement number too; with the latter, products and services might assign the number to someone who has a contractual agreement. NAS is another acronym for network access server.

SAN vs NAS Technology

A NAS includes a dedicated hardware device called the head that connects to a local area network, usually through Ethernet. This NAS server authenticates clients and manages file operations in much the same manner as traditional file servers, through well-established network protocols like NFS and CIFS/SMB.

To reduce the cost compared to traditional file servers, NAS devices generally run an embedded operating system on simplified hardware and lack peripherals like a monitor or keyboard.

A SAN commonly utilizes Fibre Channel interconnects and connects a set of storage devices that are able to share low-level data with each other.

SAN vs NAS Usage Models

The administrator of a home or small business network can connect one NAS device to their LAN. The NAS maintains its own IP address comparable to computers and other TCP/IP devices. Using a software program that normally is provided together with the NAS hardware, a network administrator can set up automatic or manual backups and file copies between the NAS and all other connected devices.

The NAS holds many gigabytes of data, up to a few terabytes. Administrators add more storage capacity to their network by installing additional NAS devices, although each NAS operates independently. 

Administrators of larger enterprise networks may require many terabytes of centralized file storage or very high-speed file transfer operations. Where installing an army of many NAS devices is not a practical option, administrators can instead install a single SAN containing a high-performance disk array to provide the needed scalability and performance.

SAN/NAS Convergence

As Internet technologies like ​TCP/IP and Ethernet have proliferated worldwide, some SAN products are making the transition from Fibre Channel to the same IP-based approach NAS uses. Also, with the rapid improvements in disk storage technology, today's NAS devices now offer capacities and performance that once were only possible with SAN.

These two industry factors have led to a partial convergence of NAS and SAN approaches to network storage.