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Photos on a phone, documents on a laptop, game installs on a desktop, a media library on an old external drive: for most households, data ends up scattered across devices with no single place to keep it and no real backup. A network attached storage device, usually shortened to NAS, solves that. It is a small always-on computer full of hard drives that every device on your network can reach, like a private cloud that lives in your home.

This guide explains what a NAS is, what you can use it for, how to choose between buying a ready-made unit and building your own, how to pick drives, how RAID works and why it is not a backup, what network and software you need, and how to set it up safely. It is based on general networking and storage knowledge rather than testing of specific products, so check the specifications and compatibility lists of any hardware you consider.

Last updated: November 1, 2026.

What a NAS Is and What It Is For

A NAS is a computer built to store and serve files. It has one or more drive bays, a processor, some memory and a network connection. You plug it into your router, and it appears on your network as a shared folder or a web interface. Unlike an external drive plugged into one computer, a NAS is available to every device, all the time, and it can run services in the background.

Common uses include:

  • Central file storage. One place for documents, photos and projects that every computer can reach.
  • Backups. Automatic backups from laptops and phones, including versions of files.
  • Media server. Streaming movies, music and photos to TVs, consoles and phones using software like Plex or Jellyfin.
  • Photo library. A private alternative to cloud photo services.
  • Shared storage for creative work. Video editors and photographers can share large files across machines.
  • Extras. Many NAS devices can run containers, download tools, home automation and surveillance recording.

A NAS is not for everyone. If you only have one computer and a small amount of data, an external drive and a cloud backup may be enough. A NAS makes sense when you have several devices, a growing library or a wish to control your own data.

NAS Versus External Drive Versus Cloud

Option Strengths Weaknesses Best for
External drive Cheap, simple, portable One computer at a time, easy to lose or damage Single-device backups and transfers
Cloud storage Access anywhere, off-site protection Ongoing fees, depends on internet, privacy trade-offs Off-site backup and sharing
NAS Shared by all devices, runs services, room to grow Higher cost, needs setup and upkeep Households with several devices and large libraries

These options work together. A common plan is a NAS for daily storage and local backup, plus a cloud service or a second drive kept elsewhere as the off-site copy. Our storage types guide explains the underlying drive technologies.

Ready-Made NAS or DIY Build?

You can buy a finished NAS appliance, or build a server from regular PC parts and install NAS software.

Ready-made NAS

  • Pros: simple setup, friendly software, small and quiet, low power use, support and regular updates.
  • Cons: higher price for the hardware, limited upgrade options, modest processors in cheaper models, and software that may restrict which drives you use.
  • Good for: most home users who want a device that works without constant tinkering.

DIY NAS

  • Pros: flexible hardware, stronger processors, more drive bays for the price, a choice of operating systems, and easy upgrades.
  • Cons: you handle compatibility, power, cooling and software setup, and the machine can be larger and louder.
  • Good for: people who enjoy building, need more power for transcoding or virtual machines, or want many drives.

Old PC as a NAS

An older desktop can become a NAS, which is a cheap way to learn. Just check that it can hold enough drives, that its fans are tolerable and that its power use is acceptable if it runs around the clock.

Choosing the Hardware

Drive bays

The number of bays decides how much storage and redundancy you can have. Two-bay units are the starting point for many homes, four-bay units are a popular balance, and five or more bays suit large libraries. Buy more bays than you think you need today, because data grows quickly.

Processor and memory

For basic file sharing, even a modest processor is fine. If you plan to stream media with real-time conversion (transcoding), run containers or host virtual machines, choose a stronger processor and more memory. Check the NAS maker’s notes on which processors support hardware video conversion, since that affects media streaming quality.

Network ports

Standard gigabit Ethernet moves about 110 megabytes per second in practice, which is enough for many uses but limits large file transfers. Models with 2.5 gigabit or 10 gigabit ports are faster, but you need a network that supports it: a compatible router or switch and the right cables. Our Ethernet cable list covers cables for fast links.

Expansion

Some NAS units offer M.2 slots for SSD caching, expansion units for extra drives, or PCIe slots. Think about what you may want later, but do not pay for features you will not use.

Power and noise

A NAS runs all day, so power use matters. Small units with a couple of drives use modest power, mostly from the drives. Noise comes from fans and spinning drives, so consider where it will live. A cupboard with no airflow can cause overheating.

Choosing Drives

Drives are the biggest part of the cost and the most important for reliability.

Use NAS-rated drives

Hard drives sold for NAS use are built to run all day, handle vibration from neighboring drives and work with RAID. Regular desktop drives may work, but they are not designed for constant operation in a multi-drive enclosure.

CMR versus SMR

Hard drives record data in two main ways. Conventional magnetic recording (CMR) writes data in a straightforward way. Shingled magnetic recording (SMR) overlaps tracks to fit more data, which can slow down during heavy writes and rebuilds. For NAS and RAID use, CMR drives are usually recommended. Check the drive’s specification sheet for the recording type, because it is not always on the box.

Capacity

Larger drives cost less per terabyte up to a point. Buy capacity for your current data plus several years of growth. Remember that RAID reduces usable space, as explained below.

Mix batches

Buying all drives from the same batch can lead to similar failure times. Some builders buy drives at different times or from different suppliers to spread the risk.

SSDs in a NAS

SSDs are quiet and fast but cost more per terabyte. In a NAS they are often used as cache or for small, fast volumes such as virtual machines, while hard drives provide the bulk storage. Our SATA SSD list covers options.

Using external drives

External drives can serve as backup targets for a NAS, or as an off-site copy that you keep in another location. See our external hard drive list.

RAID Explained (and Why It Is Not a Backup)

RAID combines several drives into one volume to improve capacity, speed or reliability. The common levels differ in what they protect against.

Level Minimum drives How it works Usable capacity Survives
RAID 0 2 Data is striped across drives All drives No drive failure
RAID 1 2 Drives mirror each other One drive’s worth One drive failure
RAID 5 3 Striping with one drive of parity All but one drive One drive failure
RAID 6 4 Striping with two drives of parity All but two drives Two drive failures
RAID 10 4 Mirrored pairs, striped together Half of the drives One failure per pair

Some NAS systems offer their own flexible schemes that mix drive sizes. These are convenient but vary by brand, so read the maker’s notes.

RAID protects against drive failure, not against everything

This point is worth repeating: RAID is not a backup. It keeps the NAS running if a drive dies. It does not protect against deleting a file by accident, a virus or ransomware that encrypts everything, a power surge that damages all drives, fire, theft or a failed controller. For those risks, you need real backups on separate storage.

Rebuilds are risky

When a drive fails in RAID 5, the array runs without protection until a replacement is installed and the data is rebuilt. That rebuild stresses the remaining drives, and a second failure during it can lose everything. Larger drives take longer to rebuild. For big arrays, RAID 6 or a mirrored layout lowers the risk.

The Backup Plan Around Your NAS

A NAS is both a place to store data and a place that needs its own backup. Follow the popular rule of three copies of your data, on two different kinds of media, with one copy off-site.

  1. Copy 1: the data on your computer or phone.
  2. Copy 2: the NAS, receiving automatic backups.
  3. Copy 3: an off-site copy, such as a cloud backup, or an external drive kept at another location and updated regularly.

Use snapshot features, if your NAS software has them, to keep earlier versions of files. Snapshots let you roll back after accidental deletion or ransomware, as long as the NAS itself is not compromised.

Networking Basics for a NAS

  • Wired connection. Connect the NAS to your router or switch with an Ethernet cable. WiFi is not appropriate for a NAS.
  • Static address. Give the NAS a fixed IP address or a reservation in your router, so devices can always find it.
  • Switch speed. If the NAS has a faster port, use a switch and cables that match. A 2.5 gigabit NAS on a gigabit switch only runs at gigabit speed.
  • Wireless clients. Laptops over WiFi will be limited by WiFi speed, not by the NAS.
  • Network layout. A simple home network is fine. Larger setups can use separate networks for cameras or guests.

NAS Software Options

The operating system makes the NAS usable. You can choose from vendor software or independent systems.

  • Vendor software. Ready-made NAS units come with a polished interface, apps and automatic updates. It is the easiest route for beginners.
  • TrueNAS. A popular free system built around the ZFS file system, with strong data integrity features. It suits users who want reliability and are willing to learn.
  • Unraid. A paid system that supports mixed drive sizes and has an easy container platform.
  • OpenMediaVault. A free, lightweight system built on Linux, with a plugin approach.
  • Windows or Linux shares. You can share folders from an ordinary PC if you only need basic file sharing.

Choose software that matches your skill and your plans. A simple file-sharing job needs very little. Running many services calls for stronger hardware and more setup.

Step-by-Step: Setting Up a NAS

  1. Plan your use. List what you want it to do: file sharing, backups, media streaming or all of them.
  2. Choose the hardware. Pick a NAS with enough bays and ports, or assemble a DIY system.
  3. Install drives. Follow the maker’s instructions and use the correct trays or mounts.
  4. Connect to the network. Plug the NAS into your router or switch with Ethernet and connect power.
  5. Install the operating system and update it. Follow the setup wizard, then install updates.
  6. Create the storage pool. Choose the RAID level that fits your drive count and risk.
  7. Create shared folders and users. Make separate accounts and limit access to what each user needs.
  8. Set up backups. Configure backups from your computers and a backup of the NAS to another location.
  9. Enable snapshots and monitoring. Turn on drive health monitoring and email alerts for problems.
  10. Test. Copy files, restore a file from a backup and simulate what you would do if a drive failed.

Security: Keep Your NAS Safe

A NAS holds your most personal data, so security matters.

  • Do not expose it directly to the internet. Avoid opening ports on your router to the NAS. Many attacks target exposed NAS devices.
  • Use a VPN for remote access. If you need access away from home, use a VPN to connect to your home network instead of exposing the NAS.
  • Use strong, unique passwords and two-factor authentication if the software offers it.
  • Turn off default accounts and unnecessary services.
  • Keep software updated. Install firmware and application updates promptly.
  • Back up to a place the NAS cannot overwrite. An off-line or off-site copy protects against ransomware.

Power Protection and Placement

Sudden power loss can corrupt data and stress drives. A battery backup (UPS) lets the NAS shut down safely. A surge protector helps protect against spikes; see our surge protector list. Place the NAS where air can circulate, away from heat sources and direct sunlight, and where you can hear if a drive begins to make unusual noises.

Running Costs and Power Use

A NAS with a couple of hard drives typically uses modest power, but it runs all day, so the cost adds up over a year. Drives that spin down when idle use less. Check the maker’s power figures and your local electricity price to estimate the yearly cost, and consider that hard drives and fans also wear out and need replacement over time.

Common Mistakes

  • Believing RAID is a backup.
  • Using SMR drives in a RAID array.
  • Exposing the NAS to the internet without protection.
  • Buying too few bays and running out of room.
  • Skipping off-site backups.
  • Putting the NAS in a closed cupboard with no airflow.
  • Ignoring drive health alerts.
  • Not testing restores until a real failure.
  • Connecting over WiFi and wondering why it is slow.
  • Skipping updates for months.

Frequently Asked Questions

Do I need a NAS at home?

Not always. A NAS is useful when you have several devices, a large media or photo library or want automatic local backups. For one computer, an external drive plus a cloud backup may be enough.

How many drives should I buy?

Two is the minimum for redundancy, and four gives a good balance of capacity and protection. Buy more bays than you need today.

Is RAID the same as a backup?

No. RAID protects against a drive failing. It does not protect against deletion, malware, theft or disasters, so you still need separate backups.

Can I use normal hard drives in a NAS?

Often yes, but NAS-rated drives are designed for continuous use and RAID. Avoid SMR drives in arrays.

Is a DIY NAS better than a ready-made one?

It is more flexible and can be more powerful, but it needs more work. A ready-made NAS is simpler and suits most people.

Do I need a fast network for a NAS?

Gigabit is enough for many uses. Faster ports help with big transfers if your network equipment supports them.

Can I access my NAS away from home?

Yes, but use a VPN or the maker’s secure remote access features rather than opening ports to the internet.

What happens if a drive in my NAS fails?

If you use a redundant RAID level, the NAS keeps working in a degraded state. Replace the drive promptly and let it rebuild, while keeping your backups current.

Bottom Line

A home NAS gives every device a shared, always-on place to store files, back up data and stream media. Choose a ready-made unit if you want simplicity, or build your own if you want flexibility and power. Buy more bays than you think you need, use NAS-rated CMR drives, pick a RAID level that matches your risk, and treat RAID as protection against drive failure, not as a backup. Add an off-site copy, keep the NAS off the open internet, protect it from power problems and test your restores before you need them.