Storage Expansion Solutions

[Checkerknight]

Other than joining a subreddit just to ask about storage solutions, I figured I'd just hop over here and see if I get any advice. 
I just purchased a HP ProDesk 400 G4 SSF to use as my new server hoster (upgraded from a Raspberry Pi 3). Nothing crazy, can supposedly handle some encoding but that wasn't the main reason, I just needed to get off the pi. 
Anyhoo, it doesn't have a lot of slots/physical storage for extra hardrives and my future goal is to have 3, maybe even 4 drives in an enclosure connected to the PC, running in Raid. 

My question then is this
- Do I need a special RAID enclosure to be able to have external drives connected to this pc running in Raid? Or can I just plug them in in any 4 bay enclosure and set RAID up on a software level?

There is probably a lot to unpack there but this is the extent of my knowledge on this matter ends. Any help/advice would be great!

[TIMFLIX1138]

From a high level position to give you some sort of answer, look into adding an HBA card to your server PC which can connect to some sort of external storage solution using an expander card. It's getting into enterprise level terminology and setups but that is the direction you need to look into. Once you get an understanding of what an HBA can do for you and how the expander fits in you can expand to your heart and wallet's content after.

I'd stay away from any self hosted RAID enclosures just from my low level networking experience they introduce more restrictive variables than the convinience can be worth.

My goal is to put 46+ drives into a smaller 4U case simple disk shelf that is pure storage (and power) connected to my main server PC. I also won't use any RAID to combine drives but that's for my personal preference and choice and most would call me a mad man. Currently I have 3 PC's in cases with a good amount of hard drive capacity just running Windows network shares. It's not idea but it does work.

[cooper.oliviia]

In my opinion, you don't need a special RAID enclosure. You can use a regular 4-slot USB or SATA enclosure and configure RAID software.

For 3-4 drives or for example light usage, software RAID with a regular enclosure works fine - just make sure each drive is accessible individually and make backups.