I've run RAID NAS for over 20 years, and have never had a drive fail before. Yeah, lucky me. Perhaps because I'm a bit paranoid and proactively replaced my drives before failure, perhaps just good fortune. This week my DS418j (SHR) had a drive crash and now I'm concerned. The failed drive passes SMART tests, but somehow the data has been corrupted. The NAS is running 2x4TB & 1x6TB drives, and provides me with more than enough storage for my current needs. Im concerned that at some point, I will have another failure of one or more drives, or just corruption of the data.

What is the better option for data protection, adding a 4th 6TB drive and making it a second storage pool, and then using Hyper Backup to keep a full backup copy of storage pool 1 or adding that same 6TB drive and going to SHR2? I refer to a 6TB drive because I plan on reformatting the crashed drive and reusing it since it appears to be otherwise physically fine. Also, I'm not sure Hyper Backup will backup to an internal drive, is that possible?

Lastly, I will explore adding an external USB drive later, right now, I'm just looking for more redundancy and a use for the existing drive.