What a NAS is and why you might build one instead of buying

A NAS (Network Attached Storage) is a box that sits on your home or office network and stores files that any device on that network can reach — your laptop, phone, tablet, or desktop. You build one by combining a NAS chassis (the empty box), a processor board, RAM, and hard drives. Building your own costs less than buying a pre-made NAS with the same storage capacity, and you control exactly which parts go inside.

The main reason to build instead of buy is cost per terabyte. A commercial 8-bay NAS from a brand like Synology or QNAP runs $800 to $1,500 before you add drives. Building the same thing from parts — a used or budget chassis, a basic motherboard, and eight drives — typically costs $400 to $700 total. You also get to choose your own drives, which matters if you want specific reliability or speed characteristics.

The trade-off is that you handle assembly and troubleshooting yourself. If a drive fails, you replace it. If the system won't boot, you diagnose it. Most people find this manageable after the first build, but it is not a plug-and-play experience like a commercial NAS.

Key Takeaways

  • A NAS chassis, motherboard, processor, RAM, and hard drives are the five core parts; the chassis determines how many drives you can install.
  • Used or refurbished server hardware costs significantly less than new consumer NAS boxes and performs the same job for home storage.
  • TrueNAS Core and Unraid are the two most common free or low-cost operating systems for a home-built NAS, and both run on standard PC hardware.
  • You need at least two drives in a mirrored setup (RAID 1) to protect against a single drive failure, though four drives in RAID 6 is more common for larger builds.
  • Network speed depends on your router and Ethernet cables, not the NAS itself — gigabit Ethernet is standard, but 10-gigabit upgrades are expensive and rarely necessary for home use.

Choosing a chassis and how many drive bays you actually need

The chassis is the metal box that holds everything. It determines the maximum number of drives you can install and whether the system fits in a closet or on a shelf. Common sizes are 4-bay, 8-bay, and 12-bay, meaning they hold 4, 8, or 12 hard drives respectively. A 4-bay chassis is roughly the size of a small desktop tower; an 8-bay is wider and deeper; a 12-bay is large enough that most people put it on the floor or a dedicated shelf.

For a first build, a 4-bay chassis is the practical starting point. It holds enough storage for most home use (8 to 16 terabytes with modern drives), costs $100 to $250 used, and takes up minimal space. If you think you will need more than 16 terabytes now or within two years, jump to 8-bay. Do not buy a 12-bay unless you already know you need it — the cost and power consumption jump significantly, and you can always add a second NAS later.

Look for used or refurbished chassis from server suppliers like SuperMicro, Norco, or Rosewill on eBay or Newegg. These are industrial-grade and last decades. Avoid very old chassis (pre-2010) because they may not fit modern motherboards or power supplies. Check the listing photos to confirm the chassis includes the power supply and that all drive bays have their trays or caddies.

Selecting a motherboard, processor, and RAM

The motherboard, processor, and RAM work together as the brain of your NAS. You do not need a powerful processor — a NAS spends most of its time waiting for network requests or disk I/O, not running calculations. A budget Intel Celeron, AMD Ryzen 3, or older generation i3 or i5 is plenty. Avoid high-end gaming processors; they waste money and electricity.

For a 4-bay build, aim for a motherboard with at least one gigabit Ethernet port (most have two), four RAM slots, and a standard ATX or micro-ATX form factor so it fits the chassis. Used server motherboards like Intel S1200 or Supermicro X9 boards are reliable and cheap ($50 to $150). Consumer boards from Asus or Gigabyte work equally well if you find them used. Pair the motherboard with 8 to 16 gigabytes of RAM — 8 GB is the minimum, 16 GB is comfortable, and more than 32 GB wastes money for a home NAS.

If you are building from scratch, budget $150 to $300 for the motherboard, processor, and RAM combined. If you are repurposing an old desktop or server, you may already have these parts. The operating system (TrueNAS or Unraid) will tell you during installation whether your hardware meets the minimum requirements.

Choosing hard drives and understanding RAID protection

Hard drives are where your actual files live, and they are the most expensive part of a NAS build. A single 4-terabyte drive costs $60 to $100; an 8-terabyte drive costs $100 to $150; a 12-terabyte drive costs $150 to $250. Prices vary by brand and retailer, so shop around. For a home NAS, buy drives from mainstream manufacturers — Western Digital, Seagate, or Toshiba — because they are widely available and have reasonable warranty coverage.

Do not use a single drive. If that drive fails, you lose everything. Instead, use at least two drives in a RAID 1 configuration, which mirrors one drive to another. If one fails, the other keeps working and you replace the failed one. A 4-bay chassis typically runs RAID 6, which uses four drives and can survive two simultaneous failures. RAID 6 is more resilient than RAID 1 and is the standard for builds with four or more drives.

For a 4-bay build, buy four identical drives of the same capacity and model. For example, four 8-terabyte WD Red drives gives you 8 terabytes of usable storage (the other 8 terabytes is used for redundancy). For an 8-bay build, buy eight drives. Matching drives simplifies replacement and reduces the chance of compatibility issues. Avoid mixing drive sizes or brands in the same RAID array.

Installing the motherboard, RAM, and power supply

Start by removing the chassis side panels and locating the motherboard tray — a flat metal plate where the motherboard screws down. Check that the I/O shield (the metal plate with cutouts for ports) is installed in the rear of the chassis. If not, slide it in from the inside before you mount the motherboard.

Install the RAM into the motherboard first, before mounting it in the chassis. Open the clips on both ends of each RAM slot, align the notch on the RAM stick with the key in the slot, and press down firmly until both clips snap closed. Then position the motherboard on the tray, align the screw holes, and fasten it with the brass standoffs that came with the chassis. Do not over-tighten — snug is enough.

Connect the power supply to the motherboard using the 24-pin ATX connector and the 8-pin CPU power connector (usually near the processor socket). Connect SATA power cables to each drive bay. Leave the drives out for now; you will install them after the system boots. Power on the system and enter the BIOS (usually by pressing Delete or F2 during startup) to confirm the motherboard recognizes the RAM and processor. If it does, shut down and proceed to the next step.

Installing drives and choosing an operating system

Once the motherboard and power are working, install the hard drives into their bays. Each drive slides into a caddy or tray, which then slides into the chassis. Connect a SATA data cable from each drive to the motherboard. Power on the system and confirm the BIOS recognizes all four drives. If any drive is missing, reseat the SATA cable and try again.

Now you need an operating system. The two most common choices for a home-built NAS are TrueNAS Core (free, based on FreeBSD) and Unraid (paid, $59 for a perpetual license). TrueNAS Core is more powerful and has no licensing cost, but it has a steeper learning curve. Unraid is simpler to set up, has better community support for beginners, and lets you add drives of different sizes to the same pool — TrueNAS requires all drives in a RAID group to be identical.

Download the operating system ISO file to a USB drive using a tool like Balena Etcher or Rufus on a Windows or Mac computer. Boot the NAS from that USB drive, follow the installation prompts, and choose your RAID configuration (RAID 1 for two drives, RAID 6 for four or more). The installation takes 10 to 20 minutes. After it completes, remove the USB drive and reboot. The NAS will be accessible from any computer on your network at an address like truenas.local or unraid.local.

Connecting to your network and accessing files

Connect the NAS to your router using an Ethernet cable. Most home routers have gigabit Ethernet ports, which is the standard for residential networks. The NAS will receive an IP address from your router's DHCP server automatically. Open a web browser on any computer on the same network and type the NAS hostname (like truenas.local) into the address bar to reach the management interface.

From there, create user accounts, set up shared folders, and configure permissions. TrueNAS and Unraid both support SMB (the protocol Windows uses), NFS (for Mac and Linux), and AFP (for older Macs). For most home use, SMB is sufficient — it works on Windows, Mac, and Linux without extra configuration. On a Windows computer, open File Explorer, click "This PC," select "Map network drive," and enter the path \\nas-hostname\foldername. On a Mac, open Finder, click "Go," select "Connect to Server," and enter smb://nas-hostname/foldername.

Speed depends on your network hardware, not the NAS itself. A gigabit Ethernet connection (the standard) transfers files at roughly 100 to 125 megabytes per second, which is fast enough for most home backups and media streaming. If you need faster speeds, upgrade to 10-gigabit Ethernet, but that requires a 10-gigabit network card ($100 to $300), a 10-gigabit switch ($200 to $500), and 10-gigabit cables — a significant investment that is rarely necessary for home use.

Frequently Asked Questions

Do I need to buy new drives or can I use old ones from a desktop?

Old desktop drives work, but they are not ideal for a NAS. Desktop drives are designed for occasional use and may fail if left running 24/7. NAS-specific drives (like WD Red or Seagate IronWolf) are built for continuous operation and have longer warranties. If you have old drives, use them for testing or non-critical storage, but buy new NAS drives for the main array.

What happens if a drive fails in RAID 6?

The NAS keeps running and you can still access all your files. The operating system will alert you that a drive has failed. You power down the NAS, remove the failed drive, install a new one, and the system automatically rebuilds the data on the new drive. This takes several hours depending on drive size, but your files remain accessible during the rebuild.

Can I access my NAS files from outside my home network?

Yes, both TrueNAS and Unraid support remote access through a VPN or a reverse proxy. TrueNAS has built-in Tailscale integration, which is the simplest option for most people. Unraid supports similar tools. Setting this up requires some network knowledge, so start with local access first and add remote access once you are comfortable with the system.

How much electricity does a NAS use?

A typical 4-bay NAS with a budget processor and four drives uses 30 to 60 watts at idle and 80 to 120 watts under load. Running 24/7, that costs roughly $30 to $60 per year in electricity, depending on your local rates. A high-end 8-bay system uses more, but the difference is usually under $100 per year.

Do I need a UPS (uninterruptible power supply)?

A UPS is not required but is recommended. It protects against data corruption if power cuts out while the NAS is writing to disk. A small UPS that keeps the NAS running for 10 to 15 minutes costs $50 to $150 and gives you time to shut down gracefully. For a home NAS, this is optional but worth considering if your area has frequent power outages.