The good news is my ReadyNAS is letting me know that there is a potential problem. The bad news is that these drives were purchased and installed in the ReadyNAS just a few short months ago.
Better safe than sorry… I’ve ordered 2 matching replacement drives to have on hand for the inevitabile failure.
Mine did that too (throw lots of those “reallocated sector count increase” errors). Of note is even a year and a half after the ReadyNAS (this was an 1100, but I think they all use the same software) started doing it, they were all still running just fine.
I eventually replaced the ReadyNAS with an XServe.