Open Source NAS
A network-attached storage box is where a household's photos and a team's working files quietly pile up into something irreplaceable, which makes the operating system running it a long-term commitment rather than a convenience: you are trusting it with the one copy you cannot regenerate. That raises the stakes on two things people skip - how the storage layer detects and survives disk failure, and whether you can actually restore after one. Open source NAS software puts that storage on hardware you own and an OS you can inspect, so your files stay reachable on your own terms instead of behind a subscription that can lapse, and the recovery path is documented rather than hidden behind a dashboard.
Copyparty
Portable file server with resumable uploads, WebDAV, SFTP, FTP, TFTP, and browser access
CasaOS
Personal cloud system for home servers with an app store and drive management
Kopia
Cross-platform backup and restore tool with encrypted snapshots, deduplication, and CLI plus GUI
OpenMediaVault
Debian-based network attached storage with a plugin framework for home and small offices
TrueNAS
ZFS-based storage platform with file, block, and object services across CORE, Enterprise, and SCALE
Rockstor
Linux and BTRFS based NAS appliance with Docker apps and RESTful APIs
Our picks
These cover the storage OS, a lighter file server, and the backup a NAS still needs.
ZFS-first storage platform: TrueNAS Builds on ZFS for snapshots, checksums, and data integrity, and shares storage over SMB and NFS for files, iSCSI for block devices, and S3 for objects. It comes from iXsystems in CORE, Enterprise, and SCALE editions and is administered from a web interface. The pick when catching silent corruption and predictable disk recovery are the priority.
Debian-based NAS for home and small office: OpenMediaVault Puts NAS administration behind a web interface on top of Debian, bundling SMB/CIFS, SFTP, SSH, rsync, and UPnP and DAAP media services, with a plugin framework to extend it. It expects full control of its machine and cannot run inside a container, a maintainable general-purpose NAS.
Portable file server, no full OS: Copyparty A single-file server that turns almost any device into a place to share files, with resumable browser uploads and access over HTTP, WebDAV, SFTP, FTP, and SMB/CIFS. Per-folder and per-user permissions plus temporary share links control access. A fit when you want file serving on existing hardware rather than a dedicated storage OS.
The backup layer storage still needs: Kopia Creates encrypted, deduplicated snapshots with client-side end-to-end encryption, writing to local disks, NAS, or cloud backends including S3, Azure, B2, and GCS. It ships both a CLI and the KopiaUI app, and a repository server lets several machines share one target. Since snapshots on the NAS are not a backup, this keeps a separate copy.
Picking a NAS you can still operate after a disk dies
Silent corruption is the failure a NAS is meant to catch, and whether it can comes down to the filesystem, not the web UI. A copy-on-write design with checksums, snapshots, and scrubs behaves very differently from traditional RAID. TrueNAS is built around ZFS for end-to-end integrity and predictable failure handling, while Rockstor uses Btrfs, which is friendlier to mixed drive sizes but needs its RAID behavior reviewed. OpenMediaVault sits on Debian and is less opinionated about the filesystem underneath. If long-term data integrity is the goal, confirm support for bit-rot detection and scheduled scrubs; if you plan to add one disk at a time, model exactly how expansion works before buying drives.
Be honest about what the box really is. Some of these are full storage operating systems that expect exclusive control of the hardware - OpenMediaVault, for instance, runs as the main OS and cannot live in a container - while others are lighter. CasaOS turns spare hardware into a personal cloud with a one-click app store, and Copyparty is a single-file server that shares folders over HTTP, WebDAV, SFTP, and SMB when you do not want a whole OS. Match that to the network roles you need: SMB for Windows and macOS, NFS for Linux and virtualization, iSCSI for block storage. Permissions get rough where SMB and NFS overlap, so test with real client machines before moving data.
Plan the failure path before you trust it with primary data. Snapshots are not backups - they will not survive theft, fire, or a destroyed pool - so keep a separate copy, which is exactly where a tool like Kopia fits, writing encrypted, deduplicated backups to another location. Confirm configuration backups include shares, users, and encryption keys, and that alerts actually fire when a drive degrades.
Related categories
Frequently asked questions
Should I choose ZFS, Btrfs, or traditional RAID?+
It depends on how you will expand, detect corruption, and recover. ZFS, which TrueNAS is built on, is strong for checksums, snapshots, scrubs, and predictable failure handling, though expansion rules are less flexible. Btrfs, used by Rockstor, is friendlier to mixed disk sizes and easy snapshots, but its RAID behavior needs careful review. Traditional RAID is familiar and fast but usually lacks end-to-end checksumming, so silent corruption can go unnoticed.
How is an open source NAS different from a plain Linux file server?+
A NAS distribution wraps storage, sharing, snapshots, users, alerts, and updates into an appliance-style workflow. A regular Linux server can do the same jobs, but you assemble and maintain the pieces yourself. OpenMediaVault and TrueNAS are useful when you want repeatable disk replacement, share management, and monitoring without turning every storage change into a custom shell session. Copyparty sits between the two: a file server you drop onto an existing machine.
Can I use mismatched drive sizes?+
Sometimes, but the storage layout decides how much capacity you actually get and how painful upgrades become. Btrfs-based systems like Rockstor handle mixed sizes more gracefully; ZFS-based ones like TrueNAS often waste the extra capacity until every drive in a group is replaced. Before buying disks, model the exact layout, usable capacity, redundancy level, and future expansion path rather than assuming the UI will make odd sizes efficient.
Which network protocols should the NAS support?+
SMB is the default for Windows and works well for many macOS users; NFS suits Linux clients and virtualization hosts; iSCSI presents block storage to another machine but is easier to corrupt if misused. TrueNAS covers all three plus S3-style object storage, while OpenMediaVault bundles SMB/CIFS, SFTP, and rsync. If you need Time Machine, media streaming, or directory integration, verify those features directly rather than assuming every platform implements them equally.
If snapshots are not backups, what should the backup plan be?+
Keep at least one separate copy, ideally off-site or disconnected, because snapshots do not protect against theft, fire, controller failure, or a destroyed pool. Kopia fits this role well: it writes encrypted, deduplicated snapshots from the NAS to local, remote, or cloud storage including S3, Azure, and B2. Whatever you use, confirm restores regularly, since a backup you have never restored is only a file, not a recovery plan.
What should I check before exposing a NAS to the internet?+
Do not expose file-sharing ports directly - SMB and NFS are not meant to face the public internet. Use a VPN, a private tunnel, or a purpose-built remote access layer with strong authentication, and keep management interfaces off the public side. Also separate remote access from backups, because ransomware that reaches your shares can often damage mounted backup targets too. A NAS reachable from anywhere is only as safe as its weakest exposed service.
Do these run on a Raspberry Pi or other small hardware?+
Several do. Rockstor runs on commodity PCs, the Pi 4, and ARM64, and CasaOS supports amd64, arm64, and armv7 boards including the Raspberry Pi and Intel NUC. Copyparty is a single-file server that runs almost anywhere Python does. Full ZFS platforms like TrueNAS are happier with more memory, especially with checksumming and many clients, so match the hardware to the filesystem and workload.