Network attached storage (NAS) is a dedicated storage device connected to your network that gives multiple users and devices shared, file-level access to the same data. A NAS combines one or more hard drives, a processor, and a lightweight storage operating system in a single box that plugs into the network over Ethernet. It receives an IP address, then shares folders over standard protocols such as SMB (Windows) and NFS (Linux) so any authorized device reaches the files. Unlike a SAN, which serves raw disk blocks, a NAS serves whole files and folders, which is why it is the common choice for home and small-office shared storage.
What Is Network Attached Storage (NAS)?
A NAS is a self-contained storage appliance whose only job is to serve files to everything else on the network. Instead of keeping data on a single computer, a NAS holds the drives, runs its own storage operating system, and connects to the network over Ethernet, so the storage no longer depends on any one machine being switched on. The defining traits of network attached storage are:
- A dedicated device: serving storage is its only function, separate from any single PC.
- A network connection: Ethernet makes the storage reachable to many devices at once.
- File-level access: it shares folders and files over protocols such as SMB and NFS.
- Multiple drive bays: several drives combine into one shared, often fault-tolerant, pool.
A NAS joins the local network like any other device and receives an address, usually from the DHCP server on the router. Because it sits on the network rather than inside one computer, it is best understood as part of a computer network, sharing data the same way other network services do.
How Does a NAS Work?
A NAS works by running a storage operating system that manages its drives and answers file requests over the network. A device asks for a file over Ethernet, the NAS reads or writes the data on its drives, and it returns the result, all using standard sharing protocols so no special client is needed. The pieces that make this work are:
- Drives store the data. Hard drives or SSDs in the NAS bays combine into one or more volumes.
- A storage OS manages everything. It controls the drives, user accounts, permissions, and apps.
- Ethernet links it to the network. The NAS gets an IP address and becomes reachable to clients.
- Protocols deliver the files. SMB serves Windows clients and NFS serves Linux, both at the file level.
Because a NAS uses file-level protocols, devices request whole files and folders rather than raw disk blocks. That request travels over the same addressing and transport layers that carry the rest of your traffic, so a NAS is just another well-behaved member of the network. A wired link is preferred for steady throughput, as covered in wired vs wireless networking.
What Is the Difference Between NAS, SAN, and DAS?
The three differ in how storage is connected and whether it is served as files or as raw blocks. DAS attaches straight to one machine, NAS shares files over the network, and SAN delivers raw blocks over a dedicated high-speed fabric for enterprise workloads.
The short version: DAS serves one machine, a SAN serves servers raw blocks at high speed and high cost, and a NAS serves files to many devices at a price a household or small office can justify. For most people outside the data center, a NAS is the storage that fits.
What Is a NAS Used For?
A NAS gives a home or office one shared storage point, which replaces scattered USB drives and manual copying. Once data lives in one place that is always on, a single set of routines can cover the whole household or team. The common uses are:
A NAS can also record footage from IP cameras around the clock. How much media, archive, or footage it holds depends on the drive capacity inside, which is the main thing to size up before buying.
How Does RAID Provide Redundancy in a NAS?
RAID combines several drives so the array keeps running when one drive fails. It spreads or mirrors data across the drives, so a single failure does not take down access to the files. The RAID levels common in a NAS are:
- RAID 1 (mirror): two drives hold identical copies, so either one can fail. Usable capacity is half the total.
- RAID 5 (single parity): data and parity spread across three or more drives, surviving one drive failure, with the capacity of all drives minus one.
- RAID 6 (double parity): a second parity block lets the array survive two simultaneous failures, using four or more drives.
- RAID 10 (striped mirrors): mirroring plus striping across four or more drives for both speed and redundancy.
RAID guards against a drive dying, not against a mistake or an attack. A deleted file, a ransomware infection, theft, or a fire hits every drive in the array at once, which is why RAID is not a backup. The capacity, speed, and fault-tolerance trade-offs of each level are detailed in the guide to RAID levels.
How Does a NAS Differ From an External Drive?
A NAS connects to the network and serves many devices at once; an external drive plugs into one computer over USB and serves only that machine. A NAS runs independently of any single PC, while an external drive is useless unless the computer it is attached to is on. The differences are:
- A NAS connects to the network and serves every authorized device at the same time.
- An external drive connects to one computer over USB and serves only that machine.
- A NAS stays on, supporting scheduled backups, remote access, and always-on apps.
- An external drive costs less and offers simple single-computer storage with no network.
An external USB drive is the right tool for single-machine storage, as the guide to adding storage to a PC describes. A NAS is the right tool when several devices need the same files at once, which a lone external drive cannot do.
How Does a NAS Compare to Cloud Storage?
A NAS keeps data on hardware you own on the local network; cloud storage keeps it on a provider’s remote servers reached over the internet. A NAS trades a one-time cost and local speed for the job of maintaining it yourself, while the cloud trades a recurring fee for offsite access and managed redundancy. The differences are:
- A NAS stores data locally on hardware you control, with no recurring storage fee.
- Cloud storage stores data on remote servers reachable anywhere with an internet connection.
- A NAS delivers local network speed, limited only by the drives and the local link.
- Cloud storage handles offsite redundancy and hardware maintenance for you.
The two work well together: a NAS can back itself up to a cloud service for offsite protection, which covers the disasters RAID cannot. The way remote services link storage and applications over the internet is covered in the overview of cloud networking.
Why Should a NAS Stay Off the Open Internet?
A NAS holds everything in one place, which makes an internet-exposed NAS a high-value target for ransomware. Attackers scan the internet for reachable NAS devices and exploit weak passwords or unpatched firmware to encrypt the drives and demand payment.
None of this means a NAS is unsafe; it means a NAS is worth protecting like any other server. The same defenses that protect the rest of the network apply here, which is the wider subject of network security.
Which Brands Make NAS Devices?
Synology and QNAP are the two established leaders, with UGREEN a fast-rising 2025 and 2026 option and Western Digital, Asustor, and TerraMaster filling out the field. The brand supplies both the hardware and the operating system, and the software is what shapes the day-to-day experience. The main NAS brands are:
- Synology: runs DiskStation Manager (DSM), widely regarded as the most polished NAS software, though its drive-compatibility policy is more restrictive.
- QNAP: runs QTS, more feature-dense and strong for 4K media transcoding and virtualization.
- UGREEN: a newer entrant offering strong hardware for the price (often 10-gigabit Ethernet out of the box), with its UGOS software still maturing.
- Western Digital, Asustor, and TerraMaster: round out the home and small-office range, from the WD My Cloud line to value-focused multi-bay units.
Match the number of drive bays and the processor to the job: file sharing and backups run fine on a basic two-bay unit, while 4K media streaming and surveillance want more bays, more memory, and a stronger processor.
NAS vs DAS vs Cloud Comparison Table
| Attribute | NAS | External Drive (DAS) | Cloud Storage |
|---|---|---|---|
| Connection | Network (Ethernet) | Direct (USB) | Internet |
| Access | Many devices at once | One computer | Anywhere online |
| Cost model | One-time hardware | One-time hardware | Recurring subscription |
| Speed | Local network speed | Local USB speed | Internet speed |
| Redundancy | RAID across drives | Single drive | Provider-managed |
| Best use | Shared home or office storage | Single-PC storage | Offsite access and backup |
How Do You Choose a NAS?
Match the drive bays, processor, memory, and network speed to the workload and the capacity you need. The specification sets both how much the unit holds and which tasks it can handle without slowing down. The factors that guide the choice are:
- Drive bays set the maximum capacity and which RAID levels are possible, from two bays up to many.
- Processor and memory decide whether the NAS can transcode media and serve many users at once.
- Network ports set the throughput, with gigabit Ethernet standard and multi-gigabit on higher models.
- Drive type matches NAS-rated hard drives for capacity or solid-state drives for speed.
A NAS for file sharing and backups runs happily on a two-bay unit with a modest processor, while 4K streaming and surveillance need more bays and processing power. Whatever the size, the unit pulls its address from the router by DHCP and combines its drives under the redundancy levels in the guide to RAID levels.
Last Thoughts on Network-Attached Storage
Network attached storage is a dedicated device on your network that gives many users shared, file-level access to the same data. It runs its own storage operating system, shares folders over SMB and NFS, and pulls together centralized backup, media streaming, a private cloud, and file sharing from one always-on point. Against the alternatives it sits in the middle: DAS serves a single machine, a SAN serves enterprise servers raw blocks at high speed and cost, and a NAS serves files to a whole household or office at a price that makes sense.
Two cautions carry the most weight. RAID keeps the array alive through a drive failure but is not a backup, so keep a separate copy, ideally offsite or in the cloud. And because a NAS holds everything in one place, keep it off the open internet and patched, reaching it remotely through a VPN rather than a public port. A NAS is one service among many on a computer network, and it is protected the same way the rest of the network is.
Key Takeaways:
- A NAS is a dedicated device that shares files over the network at the file level using SMB and NFS.
- NAS is file-level and affordable, a SAN is block-level and enterprise-grade, and DAS attaches to one machine.
- Common uses are centralized backup, media streaming, a private cloud, file sharing, and surveillance.
- RAID combines drives so the array survives a drive failure, but RAID is not a backup.
- Keep a NAS off the open internet, patch its firmware, and reach it remotely through a VPN; it is a ransomware target.
- Synology and QNAP lead the market, with UGREEN a strong 2025 and 2026 hardware-for-the-price option.
Frequently Asked Questions (FAQs)
What is NAS in simple terms?
NAS, or network attached storage, is a dedicated storage device connected to your network that gives many users and devices shared access to the same files. It holds one or more drives, runs a lightweight storage operating system, and shares folders over Ethernet using protocols such as SMB and NFS.
What is the difference between NAS and SAN?
A NAS serves whole files and folders over standard network protocols (SMB, NFS) and is simple enough for a home or small office. A SAN serves raw disk blocks over iSCSI or Fibre Channel and is built for enterprise databases and virtualization. NAS is file-level and affordable; SAN is block-level, faster, and far more expensive.
Is a NAS the same as RAID, or a backup?
No. RAID is a feature inside many NAS units that combines drives so the array survives a drive failure. It is not a backup, because a deleted file, ransomware, theft, or a fire hits every drive at once. A NAS still needs a separate backup copy, ideally offsite or in the cloud.
Should I connect my NAS to the internet?
Avoid exposing a NAS directly to the open internet. Ransomware groups such as DeadBolt have mass-scanned and encrypted internet-facing NAS devices. For remote access, disable router port forwarding and UPnP, use a VPN or the vendor’s relay service, keep firmware patched, and turn off any service you do not use.
Is a NAS better than cloud storage?
Neither is strictly better; they solve different problems. A NAS gives local network speed, a one-time hardware cost, and full control of your data. Cloud storage gives offsite access and provider-managed redundancy for a recurring fee. Many setups use both: a NAS for daily storage that backs itself up to the cloud for offsite protection.
Which brands make NAS devices?
Synology and QNAP are the two most established NAS makers, with Synology DSM widely seen as the most polished software and QNAP QTS strong for 4K media. UGREEN has become a notable 2025 and 2026 option with strong hardware for the price, and Western Digital, Asustor, and TerraMaster also produce NAS units.
