Both devices hold your files, but they behave very differently once the backup starts. Here is how they compare on cost, effort, remote access and what happens when a drive dies.
At some point a household’s photo and video library outgrows every laptop and phone in the house. The two most common ways to fix that at home are an external hard drive plugged into one computer and a network-attached storage device, or NAS, shared by the whole network. Both hold your files. They differ in what happens after the files land there, and that difference decides which one is worth your money.
What a NAS and an External Drive Actually Are
An external drive is portable storage connected through USB or a similar interface. It belongs to whatever computer it is attached to at the moment. It has no network access of its own, so anyone who wants the files has to be sitting at that machine with the drive plugged in. That simplicity is also its limit: when the drive is unplugged, nothing on the network can reach it, and if the drive dies, the data on it is gone.
A NAS is closer to a small file server than to a big USB stick. It is a standalone storage device that plugs into a switch or router, usually with wired Ethernet, and any device you designate can reach it: computers, phones, tablets, even some smart TVs. Most NAS units run a Linux-based operating system and handle the standard file-sharing protocols, so Windows, Mac, Unix and Linux machines can all use the same storage. Beyond plain storage, NAS software typically covers backup jobs, cloud synchronization, media streaming and even camera surveillance, all from the same box. Models aimed at home users commonly support up to 8TB of capacity, and USB ports let you attach extra drives later if you outgrow the built-in bays.
Upfront Costs and Ongoing Costs
The external drive wins the sticker comparison almost every time. You pay once, the drive is included, and the device draws no power when it is unplugged. For a household that just wants a second copy of documents and photos, that is the whole bill.
A NAS costs more in two stages. First, most multi-bay enclosures ship without drives, so the real price is the box plus one or more disks, and a two-bay setup with mirrored drives means buying two of them. Second, the device runs around the clock. The draw is modest, with efficient home builds commonly landing in the range of 10 to 15 watts from the wall, but it never switches off.
What a NAS can do is replace a cloud subscription. Storage plans lock you into never-ending monthly payments, and free tiers fill up fast once video enters the picture. A NAS lets you store terabytes at home without those recurring fees, and some models sync with cloud services so you can keep a copy online too. If your library is large enough that a paid cloud plan costs real money each month, that ongoing comparison shifts in the NAS’s favor over time.
Setup and Day-to-Day Effort
Plugging in an external drive takes a minute. Copying files takes a few more. The catch is that nothing happens unless you make it happen: backups get done when someone remembers to attach the drive and drag files over, which is exactly how backups get skipped. Backup software can automate the copying while the drive is attached, but the drive still has to be there.
A NAS asks for more effort on day one. You connect it to the router, create user accounts, pick your backup apps and point each computer and phone at it. After that, the daily effort mostly disappears. Modern NAS software offers one-touch backups for phones, automatic backup for PCs and Macs, including Time Machine on Apple computers, and file sync across devices with the ability to restore a document to an earlier version when something goes wrong. The trade is real: more setup now, less remembering later.
Watch for
A NAS with mirrored drives is not the same thing as a backup plan. Mirroring saves you from one failed disk, not from theft, fire, ransomware or an accidental deletion that replicates to every copy. Keep at least one copy of your important files somewhere else, such as with a cloud service.
Getting to Your Files From Outside the House
This is the starkest line between the two. An external drive has no story here: no network access means no files when you are away from the computer it is attached to. Its reach ends at the end of its cable.
A NAS is built for it. Vendors describe these boxes as personal clouds, and the phrase is accurate: you can upload and download at the speed of your home connection, reach files from any browser, desktop or mobile device, and share items through secure links instead of emailing attachments. If you keep security cameras in the house, some NAS software even records and serves that footage through a mobile app.
Opening any home device to the internet carries security responsibilities, and a NAS is no exception. Keep its operating system and apps updated, use strong unique passwords for the admin account, and think before you expose anything to the wider web. If you also keep an encrypted cloud copy of sensitive files, our explainer on how end-to-end encryption works in cloud storage covers what that protects and what it does not.
What Happens When a Drive Fails
Every drive fails eventually. With a single external drive, that event is the end of the story: one drive, one copy, nothing to fall back on. There is no redundancy and no automation to lean on, which is why a lone external drive works best as a second or third copy rather than your only one.
A two-bay NAS is designed around this problem. With the drives set up to mirror each other, a common and widely recommended configuration for home use, the data survives when one disk dies. Many enclosures use hot-swappable bays, so you slide out the failed drive, slide in a replacement and let the system rebuild the mirror. That recovery is not free: you pay for the second drive up front, and mirroring means half of your total capacity holds the duplicate. A cautious setup also pushes a copy of the NAS contents to online storage, since even a healthy array sitting in one room can be lost to the same fire or flood that takes the rest of the house.
One caution for tinkerers: the low-cost route of turning a hobby computer board into a DIY NAS is a fine way to try the concept, but RAID tends to work poorly on that kind of hardware, so any data stored there should be backed up elsewhere regardless.
Which One Fits Which Household
| Question | External hard drive | NAS |
|---|---|---|
| How it connects | USB or similar, attached to one computer | Ethernet to your router, shared across the network |
| Who can reach the files | Whoever is at that computer | Every device you designate, at home or away |
| Redundancy | None; one drive holds the only copy | Two-bay models can mirror drives and survive one failure |
| Effort | Plug in, copy, repeat forever | More setup up front, then backups run on schedule |
| Ongoing cost | Nothing while unplugged | Always-on power plus the price of spare drives |
| Suits | One computer, small budgets, occasional copies | Many devices, big photo and video libraries, remote access |
An external drive fits a household with one main computer, a modest budget and a backup habit that amounts to copying files now and then. It is also the honest answer when redundancy is not the concern and the files would fit on a single disk.
A NAS fits a house where several people, phones and tablets produce data that matters, where the library keeps growing, and where nobody wants to be the human reminder that plugs a drive in. It rewards the initial setup with automatic backups, access from anywhere and a recovery path when a disk dies. Whichever way you go, sizing the storage to what you actually keep matters, and our guide to how much cloud storage you actually need walks through that math. If you land on a NAS, our timeline for setting up your first cloud backup helps you fold an off-site copy into the plan, since the best home setup is usually one of these devices plus a copy that lives somewhere else entirely.
The essentials
- An external drive attaches to one computer over USB and has no network access; a NAS plugs into your router and serves every device you designate.
- Most multi-bay NAS enclosures do not include drives, so the real price is the box plus one or more disks, while an external drive is a single purchase.
- A two-bay NAS can mirror drives so that one failure does not take your data with it; a lone external drive is a single point of failure.
- A NAS runs day and night at a low power draw, often around 10 to 15 watts, and can replace monthly cloud storage fees for large libraries.
- Neither option alone is a complete backup plan; a copy stored outside the house, such as with a cloud service, protects against fire, theft and ransomware.
Reader questions
Can an external hard drive back up more than one computer?
Yes, but only one at a time and only while it is plugged in. Each computer has to connect to it directly, which is why households with several devices often move to a NAS.
Does a NAS remove the need for cloud storage?
It can replace paid cloud storage for big libraries, since you store terabytes at home without monthly fees. Many people still keep a cloud copy of the most important files as their off-site backup.
Is a NAS hard to set up?
It takes more work than plugging in a USB drive: you connect it to the router, create accounts and choose backup apps. After that, scheduled backups largely run themselves.
If my NAS has two mirrored drives, do I still need backups?
Yes. Mirroring protects against one drive failing, not against theft, fire, ransomware or a mistake that deletes a file on every copy at once.
We describe how services generally work; features, settings and terms change often, and they differ between companies. This is general information, not legal advice. Check the provider’s current policies and official sources such as FTC.gov.