Now as to drive configurations. I set up this way. I have a 500G drive as the core OS/TV drive. I also have 2 external 500G drives attached via USB to the core. These drives are specifically for movies, and music. My reasoning for this is:
1.) Main drive large enough to hold MD images, need a good bit of space for each MD you deploy, and a central location for my TV/Dish recordings from mythtv. Now that the installation DVD asks to if you want to save your "Settings" and "/home" this is perfect situation for upgrading/re-installing
2.) I use the external drives, mounted and maintained by LMCE, for video and music storage. This is great because when you go to rip a dvd or cd, or download a torrent, they can be stored (off site) from the core. This can also be accomplished with an internal RAID set up, just let LMCE control it. When you are actually ripping media, it asks you where you want to store it, I just choose one of my two external drives. And its as simple as that.
Internal OS/TV drive:
Things to consider here.
1. How many MD's are you going to deploy, you'll need space for them, about 20G each as a safe number.
2. TV recordings.
Here it gets tricky. If you are like me and capture your TV from a Set top box (STB), then figure 2.1G an hour. But I also have 2 Free to AIR (OTA) HD TV cards. These recordings vary in size from 5 to 7.1G an hour. If you choose to use the OS/TV setting (highly recommended) then you will need a drive to support this type of storage capacity, depending on your situation.
The reason I choose to store TV on the core, and everything else on external media is because, the core works best, at least for MythTV, to store the recordings on the core, usually down /home/public/data/videos/tv_shows_1 or whatever number your TV cards are on. For instance if you had tuner cards on moon48, then the last part of the above path would be tv_shows_48. But they are still stored on the core, even if you have a drive in the MD, which is not required.
Finally , in my case, I use Western Digital MyBook's for my external storage solution, and they can be plugged into any MD in my house, I just keep them at the core, to centralize everything. Now whenever, or wherever I am in the house, when I rip media, I point it to be stored on the external drives. And then they are available everywhere there is an MD, and they do not effect my TV recording storage.
Just my particular case. You will find that if you let LMCE manage everything for you, your media will be available anywhere in your particular deployment. And they can be easily managed from there as well.
Just my 2 cents