450GB ReiserFS LVM
When you configure MythTV, you select your folder for storing recordings. That's great if you have one monster hard drive -- or, if you use LVM. In my case, I have both :)
Basically LVM lets you put several drives together, making it look like one drive. You can add new drives to the volume, and even (carefully) remove them. I'd recommend backing up anything you have that you need before trying this. I screwed up and ended up losing some digital camera photos. Since then I was able to rebuild most of the lost data, and retrieve partial images (they're each missing about 1/4 of the image). But, in any case -- backup, backup, backup... then experiment.
I used the LVM HOWTO to setup my drive array. I chose ReiserFS because I read it's much better than ext3, and that there are really good tools for managing ReiserFS drives (which I found out when trying to rebuild lost data). I meant to use ReiserFS version 4, but I think I got 3 -- it's whatever ATRPMS gave me.
My current volume contains three 160GB Western Digital 7200 hard drives which I got at Best Buy each for $30 after the insane rebates on Black Friday. I named the volume VGForMythTVStorage, and mounted it at /var/storage.
So far, it's working great - and, if 200 hours of recording time aren't enough, then I could always add another. Hopefully I'd come to my senses by then, and start cleaning off the old episodes of Three Stooges.