Actually, if you look at URE (unrecoverable read error odds) and the numbers haven't improved in years. This means with a typical 4TB drive you're at 1 in 3 chances to have an error reading if you were to do a complete drive read. The bigger the drive the worse it looks. In short, you shouldn't be using a filesystem that doesn't do block level checksumming on large drives, and really you should be mirroring large drives now if you care about the data. Sure, the drive may not fall over and die, but what's the point if it's returning garbage without faulting?