What is network attached storage?

Whereas third-party vendors host and manage public cloud storage solutions, an organization’s internal IT team typically self-manages its NAS devices. As a result, data backups, troubleshooting, security and scaling are handled in-house. Another distinction is that NAS-stored files are accessible through a local network (although remote access is possible with additional configuring), while cloud-stored files can be accessed from anywhere through the internet.

NAS is also sometimes called a NAS box, NAS unit or NAS server. NAS boxes typically feature a drive bay, or a set of slots where teams can insert physical storage drives, such as hard disk drives (HDDs) or solid-state drives (SSDs). They might also include an accompanying operating system and applications, which enable organizations to access, share and manage the data stored on these drives.

While NAS requires a significant upfront investment in hardware, it can be more economical than cloud storage for organizations storing large, increasing volumes over the long term. Cloud costs typically scale with data volume through ongoing subscription and usage fees, whereas the per-terabyte cost of NAS decreases over time after the initial investment is made.

Network-attached storage can play a critical role in data management by facilitating centralized file sharing, data backups, disaster recovery, application storage, media file management, remote access and long-term archiving. NAS also gives organizations greater ownership of storage infrastructure and data, which is important in highly regulated industries, where data sovereignty, security and compliance are a primary concern.

While NAS technology has been around for a few decades, it has seen a resurgence in adoption over recent years. The demand for effective file storage technologies is tied to the proliferation of enterprise data, with global data volume projected to triple between 2025–2029, fueled by the rise of Internet of Things, artificial intelligence (AI), edge computing and other modern technologies.

A report from Fortune Business Insights valued the NAS market size at USD 46.97 billion in 2025. The study projects the NAS market will “grow from USD 54.7 billion in 2026 to USD 173.12 billion by 2034, exhibiting a compound annual growth rate (CAGR) of 15.50%.”

In terms of storage capacity, consumer NAS systems might contain only a few terabytes (TBs) of storage space, while small business and enterprise NAS might use dozens or hundreds of TBs. Capacity depends largely on the NAS’s intended use case.

Business use cases for NAS include:

• Data protection
• Media streaming
• Video surveillance archiving
• Collaboration and file sharing
• Hosting virtual desktops
• Cloud integration
• Testing and development of web-based or server applications

NAS boxes feature both hardware and software components. While prebuilt NAS solutions typically provide built-in components, enterprises can alternatively purchase their own server and use custom-built or open source NAS software to handle management and maintenance.

Hard disk drives (also called hard drives or hard disks) provide storage capacity for a NAS unit. As the need for data storage space increases, users can add more hard disks to meet system demand. More modern systems use flash storage (solid-state storage technology that uses flash memory chips for writing and storing data) alongside HDDs or as a stand-alone configuration.

While most NAS devices use HDDs, SSDs are a better choice for high-performance workloads. These semiconductor-based storage devices typically use NAND flash memory—named for the “not-and” Boolean logic pattern that their memory cells resemble—to retain data without a power source, providing persistent data.

For greater performance, organizations can choose SSDs that use the non-volatile memory express protocol (NVMe SSD), enabling high-speed parallel workloads. However, SSDs tend to be more expensive than hard disks. Also, older networks with limited bandwidth might be unable to accommodate SSDs’ higher throughput, creating bottlenecks.

Organizations often upgrade their network infrastructure—for example, to 10 Gigabit Ethernet (10GbE), which can process up to 10 billion bits per second—to take full advantage of SSDs’ faster speeds. For consumer NAS systems, 2.5GbE is generally considerd the practical minimum for realizing SSD throughput benefits.

NAS devices (it can be one device or multiple devices) are connected through a local area network (LAN) or an Ethernet network with an assigned IP address. Transmission Control Protocol/Internet Protocols (TCP/IP) enable data transfer, but the network protocols for data sharing can vary based on the type of client.

For example, a Windows client typically uses the server message block (SMB) protocol, while a Linux or UNIX client uses the Network File System (NFS) protocol. Many NAS devices include USB ports, which enable data exchanges with printers, external hard disks and other devices.

All NAS devices contain a CPU that manages the file system, reads and writes data, and processes and serves files. Some might also include a GPU for specialized, AI-related tasks.

NAS relies on a specialized, lightweight operating system (OS) designed to facilitate data storage and file sharing. Modern NAS OSs might also support containerization, virtualization, server management and other functions alongside primary file management duties.

Running above the OS, many NAS systems include a controller (or NAS head) that acts as an orchestration layer or control plane, processing requests and managing files stored within the NAS hardware. Often, enterprise-level NAS boxes feature two controllers.

Controller pairs can be active-active, where both controllers operate at the same time to help balance traffic load and maximize available bandwidth. Or they can be active-passive, where one controller sits in standby as a redundancy, reducing the risk of downtime.

Many third-party NAS solutions feature desktop software or mobile apps built on top of the controller that enable users to manage files, configure settings and monitor system behavior. Some also feature an app marketplace, where users can download additional tools for specialized tasks, such as data labeling, recovery services, media management and containerization.

The types of NAS are defined by their scaling mechanisms and the degree of centralization that they provide. There are two primary scaling approaches:

In scale-up configurations, organizations make upgrades to the system itself—for example, by adding expansion units, more drives, more memory or a faster CPU—to improve storage capacity or performance. This approach can be cost effective for smaller organizations. But because all upgrades take place within a single node, it’s often limiting for larger enterprises that eventually run into architectural constraints as they continue to expand.

Scale-out NAS addresses the limitations of scale-up by enabling organizations to add more servers or nodes as needed, each with their own storage and processing capacity. These individual nodes connect to form a cluster with centralized management, redundancy and failover features.

This approach enables teams to access and manage data through a unified interface, even as more nodes are added to accommodate higher traffic (horizontal scaling). Scale-out can also contribute to a more resilient NAS system because errors are isolated to the server they occurred in and are less likely to cascade to connected servers. However, scale-out often introduces more operational complexity as teams manage access, monitoring, maintenance and other tasks across disparate nodes.

NAS systems can serve a wide range of settings, from at-home or small business environments to large enterprise systems, where they are often used alongside cloud and hybrid storage solutions.

Enterprise-grade NAS is designed to support high-demand use cases, where many users need to access and write data over the same network simultaneously. This approach can support high throughput workloads, such as unstructured data archiving, video editing and CAD file management. Advanced capabilities include clustering, multi-protocol support and data compression.

Organizations often use dedicated IT resources to manage, integrate and optimize NAS systems, rather than relying on built-in configurations, as is more common with consumer NAS.

Other capabilities include:

Virtual machine support: Enterprise NAS can store virtual machine (VM) disks, where multiple virtual representations of computers are consolidated on a single physical device. It can alternatively provide storage for external VMs, which teams can manage through dedicated VMware servers.

Data protection: Enterprise NAS often features automated backups and replications, monitoring tools, failover support and advanced redundancy capabilities, which can help prevent data loss and preserve performance during intensive workloads.

Security and governance: Enterprise NAS often includes data encryption at rest and in transit, identity and access management capabilities and support for immutable snapshots (point-in-time copies that preserve a record of data writes to help prevent manipulation). Enterprise NAS solutions can also help organizations maintain regulatory compliance (with HIPAA or GDPR, for example) by providing centralized governance, monitoring and auditing tools.

Block-level support: NAS is traditionally associated with file-level access. But many enterprise-grade solutions now also support Internet Small Computer Systems Interface (iSCSI), a protocol that enables clients to access drive space at the block level. This capability is useful for workloads that expect raw disk-like storage rather than a file-and-folder structure, including database management, VM hosting, clustering and disk-level encryption.

Like enterprise NAS, consumer and small business NAS enables multiple users to access and share data across PCs and mobile devices over a network. However, consumer or small business NAS arrays generally operate at a smaller scale, feature fewer hard drive bays and require less setup and maintenance.

NAS solutions for small businesses and consumers often feature basic redundancy controls, firewalls and password protections but lack the high-level data protection or encryption features used in enterprise NAS. And because consumer NAS generally uses a stand-alone server (rather than a distributed cluster of network-connected servers), scalability is often limited.

Consumer NAS can operate as a file server (a central place to store shared files), print server, backup system and multimedia server. Many NAS solutions also enable users to access their files through the internet by using a virtual private network (VPN) or a remote access service, effectively mimicking a personal cloud. A study from SNS Insider projects the consumer segment to grow globally at a CAGR of 12.18% between 2026–2035.

Many NAS devices support redundant array of independent disks (RAID), an orchestration method that distributes data across multiple drives to improve performance, protect data or both. Each RAID level offers a different balance between performance, reliability and cost.

RAID 0 uses striping, where data is broken into blocks and distributed among multiple drives. This approach improves performance because every drive can contribute to read and write operations simultaneously, acting as a single, unified drive. However, because identical data is spread across every drive, RAID 0 does not provide fault tolerance. If an error occurs, it affects every drive in the system, creating a brittle environment where servers are highly dependent on each other.

RAID 1 trades high performance for high reliability through disk mirroring. Data is written to two or more drives at the same time, but these identical drives are isolated and operate separately. This approach provides superior fault tolerance because when one drive fails, its clone can immediately take its place. However, RAID 1 cuts an organization’s drive capacity in half because disk writes must be duplicated across at least two drives.

RAID 10 combines RAID 0 and RAID 1, incorporating both striping and mirroring so that organizations can achieve high performance and high reliability. However, RAID 10 can become expensive and inefficient at scale because, as with RAID 1, teams must duplicate data across pairs of drives.

RAID 5 stripes data across multiple drives for improved performance, like RAID 0. However, with RAID 5, the RAID controller also distributes an identical set of parity information (a guide for how to reconstruct missing data) across each drive. If any single drive fails, the NAS server can use this context to rebuild and restore the drive, improving fault tolerance.

RAID 6 is like RAID 5, except it introduces an additional parity block per drive so that each drive contains two distinct sets of recovery instructions. Double parity creates a more resilient system because it enables teams to recover from two separate drive failures, rather than just one, as in RAID 5.

While NAS is a common data storage and management choice for both enterprises and small businesses, it is not the only option available. Two common alternatives are direct-attached storage (DAS) and storage area network (SAN).

NAS enables users to access files over a shared network through wifi or an Ethernet cable. With DAS, meanwhile, the user’s computer must physically connect with the storage device to access the data it holds. Examples of DAS include a stand-alone hard disk or a flash drive, which users plug into their device through a USB or Thunderbolt port.

While DAS devices are affordable and simple to configure and maintain, they have poor scalability and can contribute to data silos inside organizations. The number of possible users is limited by the number of external ports that the drive contains, and users can only access data locally. Finally, with no centralized control plane, it can be difficult to manage and govern data across teams.

SAN systems differ from NAS and DAS by providing storage access at the block level, rather than the file level. (However, SAN can be outfitted with clustered file systems to provide file-level access.) Users typically connect with a SAN through a dedicated high-speed network such as Fibre Channel, which is unaffected by traditional network-level traffic fluctuations.

With NAS, users typically interact with a single, self-contained system (even when that system is made up of multiple redundant disks). SAN storage, meanwhile, is often spread across a distributed array of devices, including SSD and flash storage, cloud storage, specialized controllers and more.

Due to their high performance and availability, SAN systems are often ideal for managing large databases, virtual environments and enterprise-level applications, such as ERPs or CRMs. However, SAN architectures are relatively expensive and difficult to manage, making them inaccessible to smaller organizations or businesses with limited IT resources.

SAN systems are commonly used for structured transactional workloads, such as SQL database management, because they provide access at the block level, giving connected applications fine-grained control of raw disk blocks. In contrast, teams often prefer NAS deployments for managing logs, documents and media files because NAS provides immediate access to a human-readable version of stored data.

*While NAS traditionally provides file-level access and SAN provides block-level access, unified storage solutions can incorporate elements of NAS and SAN to enable both file and block level access over a shared architecture. For example, unified solutions can seamlessly move between the Network File System protocol for file level access and Fibre Channel for block level access.

In traditional NAS frameworks, the NAS unit has dual roles: It both stores data on physical hardware and provides file access controls and management. NAS gateways (or NAS heads), meanwhile, handle NAS management functions but do not contain physical drives. While they resemble an ordinary NAS system to end users, NAS gateways can connect with different types of storage solutions, such as SANs through a network connection or direct-attached storage (DAS) through a wired connection.

Instead of overhauling existing data storage infrastructure, organizations can apply the NAS gateway as a layer on top of the storage solutions they already use. And because the gateway is loosely coupled with backend storage, organizations can rapidly scale their storage without interrupting performance or connectivity.

Finally, NAS gateways enable organizations to combine the best elements of another storage solution (such as the improved performance and high reliability provided by SAN) with the convenience, security and file-level access provided by NAS.

While NAS is traditionally considered an on-premises solution, it has evolved alongside the rise of hybrid cloud, where organizations blend local and cloud solutions to optimize IT processes. Modern NAS solutions can integrate and sync with cloud services to improve data accessibility, resiliency and operational efficiency.

For example, because local network operations are often faster and more reliable than internet-based reads and writes, enterprises might prefer to use NAS solutions for workloads such as media editing, AI inference workloads and simulations, which require higher throughput.

Meanwhile, because cloud-based cold storage tends to cost less than on-premises storage, teams might orchestrate pipelines that automatically transfer data to a cloud-based storage area after a period of inactivity so that it can be archived.

In an edge-to-cloud architecture, a NAS system maintains data near the data source and sends only relevant or noteworthy information upstream because sending all raw data to the cloud is costly and often unnecessary. For example, an organization might continuously collect IoT sensor data inside a factory, store this data locally on a NAS server and send unusual spikes or anomalies to a cloud-based predictive analytics platform for further investigation.

NAS systems can support AI workloads in local and edge environments by providing secure, reliable access to training and inference data—often with lower latency and fewer performance bottlenecks than is possible with remote cloud storage over a public network.

Through access controls and audit logs that record data access, NAS servers can also give teams fine-grained control over how models access and alter data. This capability can be important for organizations that need to maintain strict compliance and auditing practices. Built-in versioning and file sharing capabilities also make NAS a good fit for some AI workloads, as multiple AI applications and instances can quickly access shared data through a local network.

However, parallel file systems, Cloud Object Storage services and other storage approaches might be better suited for real-time data processing, model training and other specialized AI tasks.

Beyond serving AI workloads, NAS systems themselves are increasingly incorporating AI capabilities, enabling automated data labeling and sorting, usage pattern analysis and natural-language file searching, among other features. Together, these tools can help reduce manual errors and accelerate workflows across various data management tasks.

While NAS provides a straightforward way to store and access files over a network, it also introduces operational challenges, including:

Benefits of network attached storage include: