(Specifically, I'm getting errors indicating that some of the index markers are missing. SMART's not putting me on 24 hour notice...yet.)
Edit: Linux has apparently decided to mark the affected partitions read-only or something. I'm going to get a new hard drive tomorrow, but I'm a little short--if anybody can PayPal me a few dollars, I'd much appreciate it.
(So much for saving that money for $trip...)
Edit 2: I've removed hda (the affected drive) from the RAID arrays; the arrays are now running in degraded mode, and will survive even a total meltdown on hda. The stuff outside the RAID array consists mostly of my e-mail (which Gmail has copies of) and software--kernel, programs, and configuration files. I'm performing a backup of all that stuff now, on the off chance the hard drive doesn't survive the night.