I haven't needed RAID for years, because my storage needs were small enough to fit on currently available drives.
Which is why my file server has a single 4TB data drive, with an external attached for mirroring on a schedule, plus a NAS also mirrored on a schedule, and Crashplan.
The NAS was recently added, and it's RAID 5, only because it was free and I had the drives sitting around collecting dust. Hopefully I can switch it to RAID 6 once deduplication is finished.
Technically only Crashplan is a real backup in my setup. The rest is just local redundancy.