Random Booting on MAC pro with 2 harddrives

[pavlov0032]

Hello!

I just realized that my mac booting from a different HD every time I restart the system. I have a mac pro with 2 HD, one 250gig in bay 1 and 500 gig in bay 2.

I copied bay1 250gig on bay2 500gig and made 500gig bootable just in case first one dies.

Now it boots sometimes from bay 1 drive sometimes form bay 2, I just realized it cause I had different desktop background set to change every day, and thought that it was same HD boot but diff wallpaper, now I realize it boots sometimes from hd1 sometimes from hd2.

When I removed bay2 drive, it boots from bay1 drive with no problem.

Anyone knows if its ok to have 2 bootable HD inside one computer?

should I make bay2 drive non bootable?

Thank you all for help!

alexei