Normally I would say software, or rather a raid-like filesystem like btrfs or ZFS. But in your specific case of funneleing it all through a single usb-c connection it is probably better to keep using an external box that handles it all internally.

That said, the CPU load of software raid it very small, so that isn't really something to be concerned with, but usb connections are quite unstable and not good for directly connecting drives in a raid.

The argument for hardware RAID has typically been about performance. But software RAID has been plenty performant for a very long time. Especially for home-use over USB...

Hardware RAID also requires you to use the same RAID controller to use your RAID. So if that card dies you likely need a replacement to use that RAID. A Linux software RAID can be mounted by any Linux system you like, so long as you get drive ordering correct.

There are two "general" categories for software RAID. The more "traditional" mdadm and filesystem raid-like things.

mdadm creates and manages the RAID in a very traditional way and provides a new filesystem agnostic block device. Typically something like /dev/md0. You can then use whatever FS you like (ext4, btrfs, zfs, or even LVM if you like).

Newer filesystems like BTRFS and ZFS implement raid-like functionality with some advantages and disadvantages. You'll want to do a bit of research here depending on the RAID level you wish to implement. BTRFS, for example, doesn't have a mature RAID5 implementation as far as I'm aware (since last I checked - double-check though).

I'd also recommend thinking a bit about how to expand your RAID later. Run out of space? You want to add drives? Replace drives? The different implementations handle this differently. mdadm has rather strict requirements that all partitions be "the same size" (though you can use a disk bigger than the others but only use part of it). I think ZFS allows for different size disks which may make increasing the size of the RAID easier as you can replace one disk at a time with a larger version pretty easily (it's possible with mdadm - but more complex).

You may also wish to add more disks in the future and not all configurations support that.

I run a RAID5 on mdadm with LVM and ext4 with no trouble. But I built my RAID when BTRFS and ZFS were a bit more experimental so I'm less sure about what they do and how stable they are. For what it's worth my server is a Dell T110 from around 12 years ago. It's a 2 core Intel G850 which isn't breaking any speed records these days. I don't notice any significant CPU usage with my setup.

Don't do a RAID enclosure, just get one that exposes the disks straight to the OS.

My guy Wendell says that Hardware Raid is Dead and is a Bad ldea in 2022

https://www.youtube.com/watch?v=l55GfAwa8RI

I read somewhere, years ago, that RAID6 takes about 2 cores, on a working server.

That may have been a decade ago, and hardware's improved significantly since then.

Bet on 1 core being saturated, min, with heavy use of a RAID6 or Z2 array, I suspect..

I'd go with software raid, not hardware: with hardware RAID, a dead array, due to a dead controller-card, means you need EXACTLY the same card, possibly the same firmware-revision, to be able to recover the RAID.

With mdadm, that simply isn't a problem: mdadm can always understand mdadm RAID's.

_ /\ _

Software, software, software! ZFS, mdraid, etc. USB is fine even with hubs, so long as your hubs and USB controllers (USB-to-SATA) are decent and not overheating.

ZFS kicks arse. It's worth learning enough to get a basic array going, with a couple of datasets and encryption. Once you get acquainted with that, you'll be using it for years to come.

Since hardware RAID is not state of the art anymore I will definetly stick with software RAID. I think I will just build a new server for the money, since an 8-Bay USB enclosure costs around 600€ and for that amount of money I can just build a new server with even better performance

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

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Your CPU should support vfio so you could pass though a PCIe sata controller to Truenas

How are those disks/the box connected to the NUC?

just my 2 cents, if youre going to do raid, buy a thing that will do it...

a nas or enclosure where the hardware does all the heavy lifting. do not build raided system from a bunch of disks... i have had, and have had friends have many failures over the years from those home brew raids failing in one way or another and its usually the software that causes the raid to go sideways.. mayvbe shits better today than it was 10-20 years ago.

its just off my list. i bought a bunch of cheap nas devices that handle the raid, and then i mirror those devices for redundancy.