I think the only data I've ever "lost" is described in some fresh threads here on the usefulness of optical and floppy media.
When I was teaching database theory, design and programming courses, I was also adding to my "computer collection." Instead of donating older machines, I'd find a way to continue using them. I needed to "learn" networking, so I created my first LAN around 1994. The practice continued after I retired: old habits die hard.
Eventually, I acquired an install disk for Windows Server (2000?). I was storing files on my server and backing up other files. This then gave way to WHS v.1 followed by WHS-2011. "Need" -- even if imagined -- trumped keeping up with full-blown enterprise server OS's.
It actually took me a while before I realized I could schedule nightly backups for myself and the fam-damn-ily from the server -- four workstations altogether. But that's the practice now, and has been for a few years.
Having worked with RAID arrays for some time, I chose a different storage strategy with drive-pooling software on the server. Stablebit allows for duplication (or even "triplication" etc.) at the folder level. So the server becomes a repository for media files that I can afford to lose as well as important data which I'll prevent losing at all costs. This alleviates the need to duplicate disks (RAID1) for redundancy.
Some of the client backups contain local client workstation user data. But in other cases, I write data and work with it directly on the server -- also duplicated, as with the client backups. Further, certain programs (Quicken, Outlook etc.) are configured to back up to the server. While those same files may be part of "Client Workstation backups," they are also backed up separately to the server by their respective programs.
Ultimately, I will then use a couple hot-swap bays with the server to do backups of different types of data every two weeks, monthly or bi-monthly depending on the intrinsic volatility of the data. These aren't "scheduled" to occur automatically, since I don't want to keep backup disks running continuously, and it might be difficult to "anticipate" the scheduled backups to mount and dismount the hot-swap caddies according to the schedule.
So I use RichCopy 4.0 -- a GUI for RoboCopy -- to make these backups on the two week, four and eight week cycles.