Recently I began outgrowing my home file server. It's an older Mac Mini with 1TB of storage space, and though it has worked well enough for several years (and through more than one OS X Server review), it's not a great choice for someone who primarily uses it as a file server. It’s not as expandable as I'd like it to be, its Fusion Drive setup offers no redundancy, and as a general-purpose computer it is rendered unnecessary by the 27-inch 2012 iMac on my desk that's still happily humming away.

My first attempt to solve the problem was with a home NAS (or Network Attached Storage) unit, a basic model with just a couple of drive bays and the ability to run a handful of media and VPN server apps if necessary. I eventually settled on a Western Digital MyCloud EX2, a basic two-drive consumer NAS that I thought would satisfy my requirements. This model gave me 2TB of mirrored storage for just under $300. I actually really liked the box itself and WD’s browser-based management software, but the wimpy ARM processor was slowing down everything from file transfers to thumbnail loading, and that didn't fill me with confidence about its future-proofness.

At this point, I had a couple of options. I could spend more money on a better, faster NAS, one that wouldn't disappoint me with its performance. Or... I could go ahead and build my own, which would give me the flexibility to build basically whatever box I wanted. Inspired by our recent articles on building a living room gaming PC and a DIY router, I decided to take the more Ars option.

What I wanted

Part of the benefit of building my own NAS box was that I could afford to be incredibly specific about what I wanted. My main problem with the Mac Mini I was using is that my upgrade options are extremely limited, so I had that at the front of my mind.

Right now , I need something with at least 2TB of mirrored storage (so two 2TB drives, total) that will perform well for backups, file transfers, and Plex media server transcoding duties.

, I need something with at least 2TB of mirrored storage (so two 2TB drives, total) that will perform well for backups, file transfers, and Plex media server transcoding duties. I’d also like to have a reasonably capable Windows PC at my desk, primarily for running and testing Windows apps and major updates but also for some very light gaming (nothing beyond what a modern integrated GPU will handle). I have a Boot Camp partition on my iMac for when I need to play heavier games, but it would be nice not to have to lose OS X every time I needed to hop into Windows for 10 minutes.

I’d like it to be flexible and future-proofed . It needs to have room and ports to accommodate more drives, and if my needs change and I want to make it do double-duty as a quad-core workstation or gaming box in a year or three, I want to be able to do that without replacing half the components.

. It needs to have room and ports to accommodate more drives, and if my needs change and I want to make it do double-duty as a quad-core workstation or gaming box in a year or three, I want to be able to do that without replacing half the components. I don’t want the costs to get out of control . I was hoping to spend somewhere between $500 and $600 on the entire project before shipping and taxes, with the understanding that around one-third to one-half of that would probably be spent on the hard drives alone.

. I was hoping to spend somewhere between $500 and $600 on the entire project before shipping and taxes, with the understanding that around one-third to one-half of that would probably be spent on the hard drives alone. Physically, I’d like it to be as small as possible without compromising any of the above goals. It needs to fit behind the door in my desk, which means I’m sticking exclusively to Mini ITX-sized components.

What I bought

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

Andrew Cunningham

With those goals in mind, these are the main system components I chose along with some of the reasons why. If you’re following along and hoping to build your own, I’ll also give a few alternatives that I consider. These should be more helpful if you’re trying to build a cheaper and more appliance-y NAS.

The case: Fractal Design Node 304 ($69.99 when I bought it, $89.99 now)

This is perhaps the most important building block of any NAS, even if you aren’t building your own—the case you put it in will dictate future expandability and the physical location where you can hide the thing.

The case I went with measures a smallish 9.84 by 8.27 by 14.72 inches (250 by 210 by 374mm), more than small enough to fit inside my desk. However, it includes a whopping six 3.5-inch drive bays, providing plenty of room for growth. Large-but-quiet fans (one of which is included) provide decent airflow, and it’s large enough to fit a reasonably powerful dedicated graphics card if I decide to add one eventually. Front I/O isn’t the best I’ve ever seen, but having two USB 3.0 ports and audio input and output on the front is enough for my needs.

The case has gotten positive (if not effusive) reviews from buyers and reviewers, which is common for decent Mini ITX cases—cable management, airflow, and actually fitting components inside are always pain points with these, and there’s really no way around it. Admittedly, the decision to go with the Node 304 would have been harder if it had cost $90 instead of $70. Keep an eye out for sales if you want this thing, but it gives you a little sticker shock at full price.

An alternate pick: Fractal Design Core 500 ($59.99)

Or, you could consider the more affordable MSRP of this alternative. This case is around the same physical size as what I chose, but there are a few key differences: the front ports and buttons are all on the top instead of the side, something I would have actually preferred for my setup. The Fractal option has an external 5.25-inch bay if you want to put a disk drive or card reader on the front, and its MSRP is significantly lower. The downside is it only has three 3.5-inch drive bays inside, though it does have three 2.5-inch bays you could use in a pinch. Ultimately I ended up going with more drive bays, but this isn’t a terrible choice if you know you don’t need that many.

The power supply: Corsair CX500M ($54.99)

Modular power supplies aren’t a requirement for mini ITX builds, but they can help cut down on cable clutter, which saves space and helps with airflow. At 500W, this Corsair model has a decent amount of headroom for future upgrades—a cheaper 430W version and more expensive 600W and 750W options are also available. I also prefer power supplies with 120mm fans, since they tend to be quieter.

An alternate pick: Rosewill Stallion Series RD400-2-SB ($29.99)

One should never, ever “cheap out” on a power supply—if it goes down, the whole computer goes down, so it’s deceptively important to get a decent one. That said, if you don’t care about modular cables and can live with less power, this Rosewill power supply is reasonably well-reviewed, comes from a company with a trusted name (Rosewill is Newegg’s house brand and “inexpensive but competent” pretty well sums it up), and has all the power cables you’d need for a decent NAS. As of this writing it costs a little over half what the Corsair power supply does.

The motherboard: Gigabyte GA-H170N-WIFI ($119.99) plus 8GB of DDR4 RAM ($38.99)

This Gigabyte board is far from the cheapest Mini ITX model to support Skylake, but it is the cheapest one with six SATA ports. It also has a bunch of other frills that are great for this kind of build. It has two gigabit Ethernet ports, a USB Type-C port (no Thunderbolt, sadly), and an M.2 slot for a Wi-Fi card that’s already populated with an Intel 8260 802.11ac and Bluetooth combo adapter. Even if you don’t plan on using Wi-Fi, integrated Bluetooth for wireless accessories is a big plus for me.

Expandability is pretty good for a board this small, too: there’s a PCI Express 3.0 slot for GPUs and other add-in cards, four of the SATA ports are compatible with the SATA Express spec, and there’s another M.2 slot on the back of the board that can accept SATA and PCI Express SSDs. That last one can free up one of the standard SATA ports for more NAS drives if you want. Since it uses Intel’s H170 chipset instead of the Z170, it’s not much of an overclocker, but I don’t care about that.

My one complaint is that there’s no DisplayPort output for easy 60Hz 4K over a single cable—I’d gladly trade away one of the two HDMI ports to gain that functionality.

An alternate pick... depends on what you want

If you want Skylake processors but don't care about the frills of my primary motherboard pick, you can get a basic Socket 1151 ITX motherboard from ASRock for $67.99. It only has four SATA ports and lacks M.2 SSD support but still includes niceties like a PCIe 3.0 expansion slot, DDR4 support, and an 802.11ac Wi-Fi and Bluetooth combo adapter (it peaks at 433Mbps instead of the 867Mbps of my main pick, though).

Here’s a potentially interesting option if your needs are more modest and you want to save money and power: ASRock will sell you a motherboard with a Braswell Celeron N3150 already integrated for $76.99, less than the cost of the CPU alone in my build.

If you don’t recognize the codename, “Braswell” denotes an Atom-related chip with a significantly weaker CPU and GPU than Skylake, so I can’t vouch for its media transcoding abilities. But it still has four cores and is totally fanless—more than enough for a more appliance-like NAS. The board includes four SATA ports and a mini PCI Express slot for a Wi-Fi card, and there’s a full-size PCI Express x1 slot you could use to add more ports or a second Ethernet port if you wanted one.

You could theoretically go with a socket 1150 motherboard and a Haswell processor, but, even though performance is fine, it’s a dead-end platform at this point. The upcoming Kaby Lake and Cannonlake processors should theoretically be compatible with socket 1151 motherboards; there’s no chance that they’ll work with socket 1150 boards. Haswell might still be appealing if you can get a good deal on the equipment, though.

Finally, you could build a system around an AMD CPU, but you shouldn’t. Intel’s advantages in CPU performance and power consumption and the general strength of its roadmap going forward are hard to argue with.

Listing image by Andrew Cunningham