My image files are all on one internal 8TB Sata SSD and backed up to 4 separate 8 TB spinning drives as exact copies of my image folder. I do that using GoodSync. I only backup the latest version of each file and don't keep previous versions because that would get to be a mess and require huge storage capacity. But yes, there is risk that that some of the files could be corrupted on the copy process (or sync) and I might never know it because I have many tens of thousands of image files.
You might be surprised, especially if you generally edit raw images in LR only, and not produce TIFF's, since those images are never changed once imported. It's one of the great features of Lightroom I think is under-appreciated. Now DNG may be a different matter if you write metadata back, as it updates the DNG and would trigger a new backup, and clearly TIFF updates every time you edit the original. But I find it a pretty small burden to do versioned backups (I use both Goodsync and Cloudberry) for images.
I tend to be paranoid and not trust software. Different people feel differently, but that distrust comes into this decision in the following way. Suppose Lightroom (or some unrelated program) got a software release that accidentally overwrite a block or two of every 10,000th file it touched. Just a mistake. That could quickly get backed up to all your backups before you even noticed, as you would not until you opened that 0.01%. With versions you get the before and after and can recover.
This sort of bad-software thing does happen. Some years ago a version of lightroom was released for Mac that just deleted all contents of the first folder alphabetically on the drive. NOT the first lightroom folder, just some other random data folder. In that case it deleted the files (though a lot of backup sync programs, including goodsync if you ask it, delete from backup if the original is deleted). I've also seen it over the years in commercial software, especially ERP systems with tens of thousands of modules, and it might not show up until some end of year process is run.
Incidentally this is why I always recommend people backup the LR catalog with their backup software PLUS let lightroom produce its own backups. This one has historical justifications -- for several versions of LR a bug corrupted every single catalog backup it made (if you had large catalogs). Every one. No apparent error. You only noticed if you tried to restore.
Software has bugs, and always will. It has gotten much better than the early days, and people get lulled into thinking nothing bad can happen because frankly it very, very, very rarely does. I just think everyone should make informed decisions (you clearly are well informed but others are reading), and hope it is useful to play out some scenarios where versioning may be needed. To me backups are best if:
- Run regularly
- Tested regularly
- Are versioned (point in time restore)
- Have some off-site copy somewhere
- Are compared to the original periodically (to detect bit rot on either side)