Every few years I update my home NAS server and try to do the best within my restrictions.
First condition is that it has to use the hardware I already have. Yes, I might buy something new so that I free up the existing HW for its bright NAS future, but I don't want to buy something specific for the NAS. While I am sure there are prebuilt systems that are much better than what I am planning, I am not building NAS only for my data. I am also building it to learn and have fun.
As second condition data has to be reasonably safe. That doesn't exclude a single drive NAS setup - I've been running one for last two years. However, together with a backup process, it has to allow for a full hardware loss while keeping data loss at the minimum. It also has to cover for the remote backup - even if it is just an HDD I keep carrying with me. And I do not have a lot of data on my NAS - currently all things I hold dear are under 1 TB in size.
It also has to be physically small enough I could take it on a plane within my clothes (good padding is important). As I am currently in the US on a non-permanent visa, that scenario is as likely as any hard drive failure. Cheap bastard in me definitely doesn't want to pay hundreds of dollars for shipping if I can just snuggle NAS in my luggage.
Last condition is that data has to be encrypted at rest. While NAS is at home I might make some things easy on me (e.g. auto-decryption at startup) but it has to be possible to keep data encrypted during transport. I am not saying TSA might be stealing stuff from luggage, I just want to be cautious.
All these things taken into consideration, I decided to use my old Intel NUC D34010WYKH as a new data storage. It is a two-core (4 logical processors) i3 device running at 1.7 GHz accompanied by 8 GB RAM and enough room for one SSD (mSATA) and one small 2.5" HDD (SATA). This nicely covered using old hardware (this was my ex-HTPC) and a small size.
For OS I decided upon XigmaNAS as it supports ZFS and it can be installed on an USB drive thus leaving my other drives fully available for data. I did consider FreeNAS as OS but NAS4Free just felt better. With ZFS I also had option of using FreeBSD or Solaris but I decided not to deal with OS updates myself. And yes, I know Linux supports both ZFS and its deranged brother BTRFS, but there are too many issues with getting either to work without issues.
As you could deduce, ZFS is going to be in charge of all data with the encryption taken care of by GELI. I did lose a bit of comfort as encryption makes web management a bit more difficult but, once scripts are in place, you don't need GUI anyhow. To allow for quick disabling of auto-decryption I would use TmpUsb drives with auto-delete. If server gets stolen this would ensure nobody can get my data.
As I wanted to have a mirror and NUC has enough place only for one 2.5" 2 TB drive, I decided to have an external 2 TB USB 3.0 drive as its partner. To make backup work I would sync daily snapshots to another local machine (manual dual boot) and to the other at a remote site. In addition to this, I would also do the weekly backup on an external USB.
Let me be the first to say I know this setup is far from the ideal with two obvious (and big) faults. The first one is not having the ECC RAM as this diminishes data security ZFS has to offer. It is not a catastrophe but not what you might want for your NAS either. Second is the need for 2.5" drives due to NUC's size. Those drives are more expensive, offer less capacity, and are slower than the bigger 3.5" brethren. This is made even worse by having an external USB drive as a part of the pool as this is making the performance worse than it should be. And let's not even go thinking about accidental unplugging...
Regardless of all its limitations, I believe this setup is going to work well for my purpose. If everything else fails it will at least give me endless hours of scripting fun needed to make all this work.
Other ZFS posts in this series:
I got a small HP MicroServer Gen8 for the same purpose, it offers 4 sata slots and ECC support for ~200€ ;)
While that server is a more powerful choice for NAS, its volume is many times that of NUC and not something I could just throw in the luggage when moving.