Some days, I forget that I'm an idiot.
For example, when I have a big Linux box, with three unused hard drives in it, and I think it might be a laugh to try to extend them using the Linux Volume Management (LVM) system. Seems like exactly what LVM's there for, and I've done exactly that before, so it shouldn't be so hard.
The idea is that rather than have to worry about pesky symlinks (is my home directory on /dev/hda1, or did I put it on /dev/sda?), you can have one glorious virtual file system that floats above the nasty details of physical hardware. For the most part, I've been happy with it.
But then I tried to add two new SATA drives to my working system (with the hope of maybe retiring old hardware at some point). And I did it badly, and the new drives ended up making my LVM volume (er, "volume group"? Man, if I don't even know how to talk about it, maybe I shouldn't be screwing with it) corrupt, unbootable, and all around bad. And then I tried removing those two drives, and that didn't work.
Long story short (and everybody says "TOO LATE"), I found this:
which tells of somebody else's similar tale of woe, and how he fixed it. Turns out, LVM squirrels away useful backup information once you start monkeying around. ("Oh, look! The meat monster is coming to corrupt our valuable data! Save yourselves!")
I believe I've put everything back where it belongs.