Working from a MacBook Pro 2.4 (Santa Rosa) with 4gb ram, running OS 10.5.7-
(All external HDs are 7200 rpm)
Shortly after our fresh install of Snow Leopard onto a new but already tested External 1.5 Seagate Barracuda (with the most current firmware), in an OWC Mercury Elite enclosure-
We installed Snow Leopard smoothly to that external HD without any issues, and it booted up from that 1.5T external HD, and worked fine.
Then, still working from the MacBook Pro, I turned on and booted another external HD (a Newertech Guardian Maximus RAID running 10.4.11 via FW800, daisy chained to the 1.5T External with Snow Leopard newly installed.
Again that's MacBook Pro <FW800> Snowy external HD <FW800> 10.4.11 RAID (booted & working from the RAID).
But when I tried to bootup up Snow Leopard, after doing the work on the 10.4.11 RAID-
It would not boot up.
Though Snowy would appear as an available Start Up disk, each time it was selected as the Boot drive,
the Internal HD OS 10.5.7 booted instead.
I changed around the cables and tried repeatedly.
Same result, no Snowy boot.
Even after the OS 10.4.11 external RAID was power down, and disconnected.
After some looking around, I found this forum:
Got me thinking.
I tried the USB, and it booted !
I tried the FW400, and it booted !
And mysteriously, at this point- I tried the FW800, and it booted !
And then, the MBP boots seemed to reliably boot from that external, via FW800.
Snow Cat needs to be taught originally how to find FW800 from the bottom up ?
Turns out, Snow Leopard doesn't like booting,
if the preceding boot was on the 10.4.11 RAID, and work was done with programs there.
So, once again, I repeated this process:
After working with programs on the 10.4.11 external HD,
the MBP would not boot the Snow Leopard external HD,
it defaulted to booting from the MBP internal HD OS 10.5 via FW800.
even though Snowy was selected for Start Up.
This was the case repeatedly.
(It would also boot from the 10.4.11 external RAID, if it were selected for Start Up.)
(In each of these tests below, I only rebooted the computer at each test. I did no work with programs on the various HDs.)
SO, once again, at this point of the process:
I plugged in that Snowy external HD via FW400,
and it booted up fine !
Then I booted up from the Internal 10.5, and tried to boot Snowy via FW800 again.
It worked !
Then I turned on the 10.4.11 RAID external HD, and tried to reboot from the Snowy external HD.
It worked too !
Then I booted from the 10.4.11 RAID, it came up fine.
Then booted from the Snowy, it came up fine.
Then booted from the Internal HD 10.5, it came up fine.
Then booted from Snowy again, it came up fine.
Then I turned off the 10.4.11 HD, booted from Snowy, it came up fine.
Then booted from the Internal, it came up fine.
Then tried Snowy one last time, it came up fine.
Anyway, the issue is:
It works fine-
Except when I do work within the programs on the 10.4.11 external RAID.
Then I have to use FW400 or USB to get it to boot once again . . .
Regardless of whether the other external HD is removed from the system.
It's some sort of flaw, and totally repeatable in testing.
Hopefully, it will be fixed soon.