One of the four drives in my Synology server is "failing," according to
the server's diagnostics. The server has been running continuously for
what, 10 years? Fortunately, I was able to find a new "exact
replacement" drive on Amazon, even though Seagate has discontinued that
particular model. I sort of recall I paid $100+ for each of the four 2TB
drives...but the closeout price on the replacement was $44.

I vaguely remember that installation of drives into the server box was
pretty simple. Hope that's not a false memory. If it is, I'll call
Fretwell and see if he can stop by with his chainsaw.