External Lacie Question

Hi Mac users,

I have two external Lacie hard drives hooked up to my Mac G4 OSX machine.
One hard drive has OS X, the other OS 9. Only one will boot up when I start
my Mac; the other doesn't. And one will just go to sleep mode all of a
sudden.
How can I make it so both start when I turn the Mac on?

Thanks for your help.