Problem adding SCSI drive on Mac OS X [Archive]

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Texasscreen

11-08-2005, 07:15 PM

I'm working my way up to (4) 15K SCSI Drives on my G4 using an Adaptec 39160 card. Starting up right now on an external drive in a Sun 611 case and have another 15K drive on the same bus that's internal. I added another drive in another 611 case and initialized the drive just fine but when this drive is online the machine refuses to start up off the Drive in the other 611 case and goes to one of the two internal drives that I have on the ATA bus. (It lets you tell it to startup off the one that I want, but just won't do it.) The drive with the OS is first out of the computer in the chain. When I take the new drive offline and return termination to the first drive it starts up off it just fine. (I want to use 4 drives because the 15K speed makes a big difference in what I do.. graphics , and 18.2G 15K drives are really cheap right now on eBay. I want to do RAID 1+0 using the Mac OS to create a mirrored and striped 36G volume. I think it will be worth the headaches.) Grady Harris

Peter M

11-09-2005, 05:15 PM

Get the termination right - remember that with internal and external drives, you need to terminate both ends, and un-terminate the host adapter because it no longer is on the end of the chain. (The host adapter normally takes care of its own terminators automatically.)

Texasscreen

11-10-2005, 12:25 PM

Not sure what you mean... I've had termination on both internal and external chains... the 611 cases seem to take care of switching their termination based on their position in the chain. What do you mean by "un-terminating" the host card? (Like I've said before here, I know that I'm in way over my head with all of this... but I really do want to learn.) Thanks for your help!

Peter M

11-11-2005, 02:33 PM

You need to make sure that you got exactly two terminators active on each SCSI channel. If you're using both internal and external connector on one channel, then terminate each cable end, and make sure the host adapter itself disables its onboard termination.
External cases normally do not auto-terminate btw. Consult its manual to find out.