What is network-attached storage (NAS)?

Network-attached storage (NAS) is an alternative to storage area networks (SAN), and provides access to shared storage via network protocols. Popularly, NAS can use TCP/IP networks for transferring both data and storage traffic. NAS utilizes file-level storage over object-based storage. Because NAS uses TCP/IP networks, it does not rely on a separate SAN fabric, which cost effectively allows scaling data and storage networks using the organization’s existing network hardware.

Two reasons for this cost effectiveness are because data networking hardware is significantly cheaper than storage networking hardware, like SAN fabrics and storage. And, the reuse and sharing of data infrastructure and storage networking infrastructure allows admins to quickly support both requirements without additional training.

For users, the difference between NAS and SAN are few.  NAS will appear as a file server on workstations, whereas SAN will appear as a mounted drive. Natively, NAS also allows concurrent access to shares. While these differences may not seem significant, the performance difference is great. Because SAN and its network fabric are designed for storage and access performance, it offers much greater storage throughput than NAS. Again, NAS must rely on the existing TCP/IP network.

For many small businesses, though, they do not require the performance throughput offered with SAN. Helpfully, NAS remains scalable, and can act as a private cloud. Because of this cloud characteristic, NAS data may be accessed remotely through network connections. Incidentally, this allows for teams to integrate remote working into their work schedules, able to access work at any time, from anywhere.

Three general components are utilized in NAS configurations: standard hardware, specialized software, and data transfer protocols.

Dedicated NAS hardware, often called NAS box, NAS unit, NAS server, or NAS head, contains storage drives and disks, processors, network adapter, and memory (RAM). Together, these form the hardware component of a NAS unit which is where data will be stored and accessed via network-based communications.

Software is the key difference between a NAS unit and simply attaching a general server to a network to house and share files. First, NAS units use a paired down OS, which runs the NAS software that is typically embedded on the hardware to improve performance and security. A general purpose server operates standard OSes, with all its overhead, whereas a NAS unit only handles data storage and file sharing requests, greatly improving efficiency and performance.

The final component is the set of protocols that the NAS unit will be configured to use in connecting and transferring data across the network. Because NAS attach to TCP/IP networks, TCP/IP are the fundamental protocols for transferring data. TCP/IP rounds up packets of data, and then packages them with an address to be sent over the network.

Because when NAS units are connected to networks they can use a file-sharing protocol, they appear as file shares on workstations. File-sharing allows multiple users access to information and files as if it were on their own system. Each OS, Windows, Linux, and Apple, use a separate file system protocol for sharing:

• Network File System (NFS): Typical to linux and unix based systems, NFS is a vendor agnostic protocol, compatible with most hardware, operating systems, and networks.
• Common Internet File Sharing (CIFS)/Server Message Block (SMB):  CIFS/SMB are windows specific protocols, which offer other features such as sharing printers.
• Apple Filing Protocol (AFP): AFP is Apple’s proprietary file sharing protocol, formerly known as AppleTalk.

The main benefit of NAS is in providing scalable network storage capacity that is easily integrated into most network setups.

• Scalability — NAS provides a way for IT teams to easily and quickly scale storage capacity. Also, beneficially, IT teams are not required to bring the network down in order to add more hard disks to the NAS unit.
• Performance — While SAN may be the best performing storage networking configuration, in regards to throughput, the same benefits occur with NAS, namely dedicated file serving and sharing which improves throughput . Because NAS software is paired down to only those specialized functions for delivering data, decreased overhead and complexity helps to improve performance.
• Accessibility — Because NAS “attaches” to the network, all network devices have access to the NAS unit.
• Resilience and Fault Tolerance — NAS units can support technologies that improve resilience, like disk replication, redundancy arrays, and erasure coding.
• Easily Integrated — NAS units are easily installed, and can be delivered as pre-loaded appliances that can simply be added to the network.

NAS is often a better solution for businesses over directly attached storage options. But the advantages of NAS must be carefully weighed with its disadvantages when deciding on data storage options.

Advantages:

• Simultaneous multi user access to NAS
• File sharing among multiple users and devices
• Remote access options
• Application options for web-enablement and additional functions
• Scalable through the additional of more NAS devices

Disadvantages:

• I/O transfer speeds are slower than DAS
• Must be integrated into a network
• NAS chipsets and firmware adds functional variations to different devices

Network Attached Storage is a device, and not a cloud configuration. While clouds do provide scalable storage to consumers, and NAS can be a part of that configuration, NAS is storage, and lacks the elements that create clouds, namely the hypervisors, and virtualization software. When accessing a company NAS via the internet, in reality the user is accessing the company network to gain access to the NAS unit on that network.

NAS serves many use cases in both the home/small business and at the enterprise level, all with the overarching need for flexible and scalable data storage, available via TCP/IP networks, including over the Internet. NAS allows users to ultimately share data and collaborate more effectively, for example, as remote teams in different timezones.

In the household, NAS may be used for storing large files, typically personal multimedia, or for supporting the recording of streaming video. Adding data storage capacity with a NAS also opens other applications:

• Supports security and surveillance systems
• Supports smart TVs, streaming digital video recording
• Supports smart houses and connected devices, IoT devices
• Supports home computer development workstations
• Supports private cloud deployments

While the power of enhanced storage in the home enables many new, “futuristic”, technologies, NAS in the enterprise supports critical systems, some that may go unnoticed by the general public, like healthcare testing, or food production, but are never-the-less improved through the help of NAS. Some applications include:

• RAID (Redundant Array of Independent Disks) configurations pull multiple NAS into a single logical unit to boost redundancy and performance and achieve high availability.
• NAS are used to partition data for multiple uses, for example, testing and development, running independent services like email or messaging programs, running independent operating systems, etc.

Providing company wide file sharing, or more granularly, to departments, groups, teams, roles, etc.

Understanding the main differences between direct attached storage (DAS), storage area network (SAN), and software-defined storage (SDS) supplies context for which situations benefit from network attached storage (NAS).

Direct Attached Storage (DAS) — Typically the least expensive option, DAS storage provides block-level storage that can be connected directly, and most commonly, via USB, or eSATA. This differs from NAS in that accessing the DAS unit does not require data transfer over the network. While this configuration provides the faster transfer speeds, only the host connected to by the DAS unit can access it.

Storage Area Network (SAN) — Compared to DAS units, SANs reside on the opposite side of a storage device spectrum. SANs are typically deployed in enterprise data centers as a high-end storage solution. Like DAS, SANs provide block-level storage, however, it resides on its own network, sometimes referred to as the SAN fabric. The SAN and fabric configuration is optimized for high-performance, and complex use cases, and is critical for enabling high availability (HA).

Software Defined Storage (SDS) — Based on the concept of software defined networks (SDN), SDS utilizes software to bring together storage resources from multiple locations. SDS, like SDN, shares the benefits of maximum data storage flexibility, with the ability to handle dynamically changing application requirements. Additionally, SDS creates a centralized control and management of enterprise storage, beneficially, with the ability to create and apply policies across multiple vendors, empowered by automation to enforce such policies

Within the NAS category, solutions can be divided into three groups based on capabilities, performance, and capacity.

• High-End / Enterprise — Enterprise level NAS are used in data centers to store massive volumes of data. These devices will likely end up serving cloud services to consumers. Because of this, they will utilize cloud technologies, like virtualization and clustering of NAS devices to ensure optimized performance.
• Midmarket — Midmarket NAS separates itself from low-end NAS by capacity, typically within the mid-upper terabyte (TB) range. These devices don’t meet the needs of high-end NAS applications, namely they don’t allow the use of clustering in optimizing storage.
• Low-End / Desktop — While there are home use options for NAS, many disagree that NAS is a desktop application, rather and truly, NAS drives appear in RAID configurations (which itself is a virtualization configuration, and more enterprise application than desktop). These NAS desktop options are typically in the low TB range, and are becoming obsolete as this market is adopting cloud models to replace home storage.