When I boot, it waits, then I see gray Stop sign, then it boots
I've got a Mac Pro running 10.6.8. I have an SSD internal drive in there that is selected as my boot disk. I also have a clone of this (external USB) and an internal RAID1. When I turn on the machine, the gray screen has the rotating circle of gray bars for a while (minutes), and then the gray stop sign (circle with a line through it) appears. After that, it boots from the SSD very quickly, as it should. What I'd like to know is, what else can I do (other than selecting it as my boot drive in Preferences) to make it go to that right away instead of doing whatever it's doing that causes it to delay, then fail, and only then go to the correct disk. It's weird because these other drives are also bootable so if that's what it was trying, it should be coming up in the wrong system. But it's not. What is it doing, and how do I make it go to the SSD right away?