File got corrupted on Fileserver, Permanent way to avoid this issue

In my network I have a Fileserver with 2x4 TB disc capacity. I run debian on it. The initial configuration was to put the two HDDs on Software RAID 1. This setup worked perfectly fine for about 3.5 years. It worked until I needed a large zip file containing a game. A friend was at my home and we wanted to play this game. I allready had the file on my computer, he copied it from the Server. When he wanted to unzip it, WinRar throw some errors. He did not have any write permissions, so it was not possible that he or I had modify the file by mistake. A quick comparison between the checksums confirmed that both files were different. I replaced the currpeted file on the server with the one on my computer and we could play. It was my first encouter of Bit rot. A not funny experience, because I knew that possibly more files are corrupt. I then needed a better and more robust solution to store my important files.
No answers yet.