[G4] EIDE and Ultra ATA RAID

[Philip J Robar]

On Apr 27, 2005, at 6:23 PM, shopdog wrote:

> Philip:
>
> Thanks for the information.  I will try to find some of those  
> tutorials. I'm a little wary about using a RAID system. I asked the  
> question because I tested a mirrored RAID system once, in the  
> following manner. Maybe you all can educate me on what I should  
> have done instead...
>
> I set up 2 firewire (wall powered) hard drives (same make, same  
> size) in a mirrored array using OS X's disk utility. I saved a file  
> to the array. I restarted the computer (I have a 12" PowerBook)  
> with both drives attached, and the array and the file were fine. I  
> shut down the computer, and disconnected one of the drives. I  
> started the computer, and the system showed the array as corrupted,  
> and of course, I couldn't get to the file. I shut down the  
> computer, reattached the drive (so both drives were attached as  
> before), and then started the computer. The system showed the array  
> still corrupted.

In theory this should have worked. There's any number of things that  
could have gone wrong: a bug in Apple's raid implementation, OS X not  
flushing data to the firewire drives correctly - especially at  
shutdown time, a bad interaction between OS X and the firewire bridge  
firmware, etc. However, with 10.3.9 and up-to-date firmware I would  
expect this set up to pass this test. One thing that you could try is  
to always explicitly unmount the firewire drives before shutting down.


> I was wondering, if the drive I had disconnected could not be  
> replaced (say it had mechanically failed), how would I have been  
> able to get the file off the one drive? Or would I have to get a  
> new drive and rebuild the array to get the file.

The remaining drive should be able to keep running on its own. When  
the failed drive is replaced you should be able to rebuild the array  
with the RAID software.


Phil