How it works

SMB (Server Message Block) is the file- and printer-sharing protocol Windows speaks on a LAN. A client (File Explorer, Finder with SMB enabled, a phone app) asks a server for a share by name: \\NAS\media on Windows, or smb://nas.local/media on macOS/Linux. The server answers with directory listings, file opens, locks, and writes over TCP (modern stacks use port 445). Older NetBIOS/LAN Manager eras used other ports; home gear today is almost always SMB over TCP with optional signing and encryption.

On a NAS, the appliance runs an SMB server (Samba on most Linux-based OS builds, or Synology/Qnap/Asustor wrappers around similar stacks). You create users, map folders to shares, set read/write ACLs, and optionally turn on SMB3 encryption or require signing. Windows can also host SMB shares from Settings, and a Raspberry Pi or mini PC can do the same with Samba. Version matters: SMB1 is obsolete and unsafe; SMB2/SMB3 are what you want enabled. Multichannel and RDMA show up on bigger Windows Server deployments; home boxes mostly care about SMB3, stable auth, and not leaving guest shares wide open.

When it matters

It matters whenever a Windows PC, Mac, or phone needs a network drive that feels like a local folder. Time Machine and Windows Backup targets, media libraries Plex or Jellyfin read over the LAN, and office documents on a shared project folder all ride SMB in most homes. Prefer a dedicated NAS when you want always-on shares, snapshots, and RAID; a USB DAS with UASP is fine for one desk but is not multi-user SMB. Skip guest-everyone shares on a flat home Wi-Fi if guests or IoT devices share the same subnet.

Shopping traps: leaving SMB1 enabled for one old printer, buying a NAS without checking whether DSM/QTS/ADM exposes SMB3 signing/encryption toggles you care about, and confusing a USB dock (hot-swap bay) with a network share. Cable and switch speed still cap throughput: gigabit tops out near 110 MB/s, while 2.5GbE NAS ports help when disks and clients keep up.

A mainstream 2-bay NAS that speaks polished SMB via DSM, a cheaper 2.5GbE 2-bay alternative, and a confirmed-CMR 4TB NAS drive to fill the first bay.

The Synology DiskStation DS225+ 2-Bay NAS (Diskless) is the polished DSM path for Windows/Mac SMB shares, backups, and light Plex on a 2.5GbE home LAN.

The Asustor Drivestor 2 Gen 2 AS1202T 2-Bay NAS (Diskless) is the budget 2.5GbE two-bay box when you still want SMB shares and Btrfs snapshots without Synology pricing.

The WD Red Plus 4TB NAS Internal Hard Drive, CMR (WD40EFPX) is a confirmed-CMR SATA NAS drive so the first share array does not inherit SMR rebuild pain.

Start with What Is a NAS? for the appliance that usually hosts SMB. Pick an array layout with RAID Levels Explained, then back the shares up with The 3-2-1 Backup Strategy. Drive health basics live under SMART; bay mechanics under Hot-swap and JBOD.