[G4] EIDE and Ultra ATA RAID

[shopdog]

Phil:

Thank you for the insight.  A few things I can't seem to find definite 
answers on, although you hint at one of them...

1) You say the remaining drive should be able to keep running on its 
own.  Do you mean that it should have a full directory, and therefore I 
should be able to treat it as a single drive (i.e., as if it was never 
part of an array), and therefore the file should show up and I could 
get the file, and then continue using the drive as a single drive?  Or 
do I need to rebuild the array, and only then be able to get to the 
file?  Or can I rebuild the array at any point (presumably the array 
would be rebuilt so that any files I have added since the failure would 
then be duplicated to the new second drive)?  Hopefully I'm asking the 
question clearly.

2) How does one set up a JBOD, and can OS X Disk Utility do it (My 
guess is no.)?  If one drive in a JBOD fails, is it only the data on 
that drive that is lost?  That is my understanding, since files are 
saved sequentially as the disc space fills up (the system uses one 
drive first, then the next, etc.), as opposed to saving files at random 
places across the JBOD.  Does a JBOD ever save parts of a file on one 
of the drives and part of the file on another drive, so that if one 
drive failed you would lose the file?  Or does a JBOD make sure that a 
file never spans more than one drive?  (My guess is it spans drives 
sometimes.)

Thanks again...

On Apr 29, 2005, at 3:58 AM, Philip J Robar wrote:

> 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
>
>
> _______________________________________________
> G4 mailing list
> G4 at listserver.themacintoshguy.com
> http://listserver.themacintoshguy.com/mailman/listinfo/g4
>
> Listmom is trying to clean out his closets! Vintage Mac and random 
> stuff:
>         http://search.ebay.com/_W0QQsassZmacguy1984