Just had a disk go disabled when I was writing to an unrelated disk (same share folder on both disks, though; hardly any read/writes on the disabled disk since the system was last booted up a couple of days ago, just noticed it disabled when it threw up 2 error messages a little while ago).
My instinct is to replace it, but the lack of writes made me think something may be up, and since it's been close to 2 months since my last parity check (was planning on one this weekend), I'd lik