Ansible-NAS currently assumes you know your way around a server. This page is an overview for absolute NAS beginners so they can decide if it is right for them.
The big picture
To start off really simple: A NAS (Network Attached Storage) is a server mostly for home or other small networks that offers file storage. It's usually a small box that sits in the corner and runs 24/7. These days, a NAS doesn't just only handle files, but also offers other services, for instance video streaming with Plex or Emby. You can buy consumer NAS boxes from various manufacturers where you just have to add the hard drives, or you can configure your own hardware and use open-source software as the operating system.
One example of the second variant you'll see mentioned here is FreeNAS. It is based on FreeBSD, which like Linux belongs to the family of Unix-like operating systems. One strength of FreeBSD/FreeNAS is that it includes the powerful ZFS file system (OpenZFS, to be exact). However, it does not support the Docker containers the way Linux does. Also, the Linux ecosystem is larger. On the other hand, very few Linux distributions include ZFS out of the box because of licensing issues.
Ansible-NAS in its default form attempts to have the best of both worlds by using Docker on Linux with ZFS. This is possible because the Ubuntu Linux distribution supports both technologies. As the name says, Ansible-NAS uses Ansible server automation which is usually deployed on big multi-machine enterprise systems, not small home servers the size of a breadbox.
Before you take the plunge
The commercial NAS vendors try to make setting up and running a NAS as simple and painless as possible - for a fee, obviously. The open-source NAS software providers have lots of resources to help you get started with your own hardware. FreeNAS for instance comes with extensive documentation, good introductions to ZFS and other topics, and a large community to lean on.
With Ansible-NAS, at this point at least, you're pretty much on your own. Though there is a Gitter chat room (see support), you're expected to have some familiarity with the technologies involved and be able to set up the basic stuff yourself.
As a to-do list, before you can even install Ansible-NAS, you'll have to:
Choose, buy, configure, and test your own hardware. If you're paranoid (a good mindset when dealing with servers), you'll probably want an uninterruptible power supply (UPS) of some sort as well as SMART monitoring for your hard drives. See the FreeNAS hardware requirements as a guideline, but remember you'll also be running Docker. If you use ZFS (see below), take into account it loves RAM and prefers to have the hard drives all to itself.
Install Ubuntu Server, currently 20.04 LTS, and keep it updated. You'll probably want to perform other basic setup tasks like hardening SSH and including email notifications. There are various guides for this, but if you're just getting started, you'll probably need a book.
You will probably want to install a specialized filesystem for bulk storage such as ZFS or Btrfs. Both offer features such as snapshots, checksumming and scrubbing to protect your data against bitrot, ransomware and other nasties. Ansible-NAS historically prefers ZFS because this lets you swap storage pools with FreeNAS. A brief introduction to ZFS is included in the Ansible-NAS documentation, as well as an example of a very simple ZFS setup.
After that, you can continue with the actual installation of Ansible-NAS.
How to experiment
The easiest way to take Ansible-NAS for a spin is in a virtual machine, for instance in VirtualBox. You'll want to create three virtual hard drives for testing: One of the actual NAS, and the two others to create a mirrored ZFS pool. This will let you experiment with installing, configuring, and running a complete system.