What is a NAS and is it better than an external drive?

A NAS (network attached storage) is a small dedicated computer containing one or more drives, connected to your network rather than to a single machine. An external drive connects directly to one computer over USB.

What a NAS does that an external drive cannot:

Multiple devices access it simultaneously, over the network, without anyone being plugged in.

It runs continuously, so scheduled backups from several machines happen automatically without anyone remembering to connect anything.

RAID redundancy. Two or more drives can be configured so that one failing does not lose data. This is the main technical advantage, and it needs a crucial caveat below.

Services. Most NAS units run applications — media servers, photo libraries with indexing, file sync comparable to a cloud drive, surveillance recording, and containers for other software.

Remote access from outside the home.

Where an external drive wins:

Cost. Dramatically cheaper, with no enclosure, processor or software.

Simplicity. Nothing to configure, no network to secure.

Portability, which matters for offsite copies.

Speed for one machine — a directly connected SSD over USB is typically faster than gigabit networking.

The caveat that matters most: RAID is not a backup. Redundancy protects against drive failure and nothing else. It does not protect against accidental deletion, ransomware, file corruption, theft, fire or flood — all of which are replicated instantly across the array. A NAS should itself be backed up, ideally to the cloud or to a rotating offsite drive.

The standard guidance remains 3-2-1: three copies, on two media types, one offsite.

Security note. A NAS is an internet-adjacent computer. Several ransomware campaigns have specifically targeted consumer NAS devices exposed to the internet. Keep firmware updated, disable unnecessary services, avoid direct port forwarding, and use strong credentials with two-factor authentication.