Learn NAS - Core Concepts & Main Architecture

#Introduction

Now that you understand the history and the reasons for needing a NAS, it's time to break down how it works internally. Episode 2 covers the core concepts and main architecture of a NAS: the hardware model, the software platforms, and the three layers of architecture working behind the scenes.

The key concept in this episode is that a NAS is really a storage server that runs several layers of responsibility: the physical storage layer that manages disks, the sharing layer that speaks network protocols, and the management layer you use through your browser. Understanding this separation will make navigating any troubleshooting much easier later on.

By the end of this episode you'll be able to tell dedicated appliances and software NAS apart, compare TrueNAS SCALE and OpenMediaVault, and explain the data path from raw disks to shares accessed by clients.

#The NAS Model: Dedicated Appliance vs Software NAS

#Dedicated Appliance

A dedicated appliance is a finished product like Synology, QNAP, or ASUSTOR: hardware and software are designed as a single unit. The advantages are obvious — a smooth out-of-the-box experience, vendor warranty, and a user-friendly interface.

The downsides: appliances tend to be expensive per terabyte, hardware is hard to upgrade, and there is often lock-in with the vendor ecosystem. For a homelab that wants full control, this can be an obstacle.

#Software NAS on General-Purpose Hardware

Software NAS platforms like TrueNAS SCALE and OpenMediaVault are installed on general-purpose hardware you assemble yourself. You're free to choose the CPU, RAM, HBA, NIC, and number of disks. Full control, lower price per terabyte, and components that can be upgraded one at a time.

The trade-off is that you're responsible for hardware compatibility and maintenance yourself. This is the path most homelab enthusiasts take, and it's the focus of this series.

lscpu
lsblk
ip link

The lsblk and ip link output shows the disks and network interfaces managed by the system. These are the raw materials of a software NAS.

#Comparing the Main Platforms

#TrueNAS SCALE: ZFS and Full Features

TrueNAS SCALE is iXsystems' open-source platform, Debian-based, with ZFS as its only filesystem. Its strengths are data integrity (checksums, copy-on-write), snapshots, replication, and an increasingly rich application ecosystem.

The features that make it popular in homelabs and enterprises: Apps based on Docker/Kubernetes, VMs with KVM, the TrueNAS API, and High Availability options in the Enterprise version. The current stable version is 25.10.2 (Goldeye).

#OpenMediaVault: Light and Plugin-Based

OpenMediaVault (OMV) is a lighter Debian-based alternative. It doesn't force ZFS; you're free to use ext4, btrfs, or add a ZFS plugin. The plugin-based approach makes OMV easy to customize and resource-efficient, well suited for NAS setups based on a Raspberry Pi or an old PC.

A quick comparison of the two platforms:

• Filesystem: TrueNAS requires ZFS; OMV is free to use ext4/btrfs/ZFS.
• Resources: TrueNAS needs more RAM; OMV is very frugal.
• Features: TrueNAS has built-in Apps and VMs; OMV goes through plugins.
• Fit: TrueNAS for data-heavy and production workloads; OMV for light and flexible setups.

#The Three-Layer NAS Architecture

#Storage Engine

The bottom layer is the storage engine: the filesystem and volume management. On TrueNAS SCALE this is ZFS with its concepts of pools, vdevs, and datasets. On OpenMediaVault it can be ext4 with LVM, btrfs, or ZFS through a plugin. This layer is responsible for how data is written to disk, checksums, and protection against disk failures.

zpool status
zfs list

The zpool status command shows pool and vdev health, while zfs list lists the datasets. Both will become your main tools starting in episode 5.

#Sharing Layer

The second layer is the sharing layer: the set of protocols that serve storage to clients over the network. The main protocols are:

• SMB/CIFS: the file-sharing standard for Windows, macOS, and Linux.
• NFS: the file-sharing standard for Unix-like systems and virtualization.
• iSCSI: block storage that looks like a local disk on the client.
• SFTP/FTP: file access via transfer protocols.

Each protocol plays a different role. SMB for day-to-day file sharing, NFS for virtualization shared storage, and iSCSI for block-level needs.

#Management UI and Hardware Integration

The top layer is the management UI: the web interface where you create pools, configure shares, users, backups, and monitoring. TrueNAS SCALE serves a modern Angular-based UI; OpenMediaVault has a simpler Workbench.

All the layers run on top of hardware: disks are connected through an HBA (Host Bus Adapter), a NIC connects to the network, and RAM/CPU process every operation. This architecture can be visualized as: hardware hosts the storage engine, the storage engine hosts the sharing layer, and the management UI governs both.

#The Data Path from Disk to Client

A simple simulation: a Windows client requests a file over SMB. The flow is:

1. The client sends an SMB request to the NAS IP.
2. The sharing layer translates it into access to a dataset in the pool.
3. The storage engine reads the data from disk with checksum verification.
4. The data flows back through the NIC to the client.

ss -tn

The ss -tn command shows active TCP connections, including SMB and NFS sessions to the NAS. This is a quick way to verify an ongoing data flow.

#Closing

In this episode 2 you understood the dedicated appliance versus software NAS model, compared TrueNAS SCALE and OpenMediaVault, and mastered the three-layer NAS architecture: storage engine, sharing layer, and management UI running on top of hardware.

Key takeaways:

• Software NAS gives you full control over general-purpose hardware; appliances are smoother but pricier.
• TrueNAS SCALE requires ZFS; OpenMediaVault is flexible and light.
• NAS architecture consists of a storage engine, a sharing layer, and a management UI.
• SMB, NFS, and iSCSI serve different file and block needs.
• Data always flows through the storage engine before being sent to the client.

In the next episode, episode 3, we'll plan the hardware and storage — from CPU choices, ECC RAM, HBA, 10GbE NIC, to a disk layout that balances budget and reliability. Make sure you understand this three-layer architecture, because every hardware decision supports it.