Cheap System for Backing up Data

[cyclones]

Hello all. So I currently have a Synology DS218+ that is used mostly for backing up my computers data. I have it configured in RAID mode with total storage size around 6TB. However I am looking to create a redundancy solution in case the NAS or drives would ever fail. I have a lot of hard drives laying around and want to build a cheap computer that is able to have more than 4+ HDD's installed in the system so I can use those to backup my data. I came across Storage Spaces in Windows where it lets you use multiple drives to back up data. I'm wondering if someone could provide a cheap computer solution that I could utilize this or if there's an easier way of doing it with Linux so I don't have to worry about the licensing for Windows. Essentially the data would copy from my PC's to the NAS and then from PC's to the redundant computer backup. Any help would be greatly appreciated!

 

[Joe C]

You can use an older pc you have or you can get a used pc cheap on ebay or craigslist...
https://www.bestbackups.com/diy-nas-old-pc/