RAID questions

CrackedButter

macrumors 68040
Original poster
Jan 15, 2003
3,221
0
51st State of America
I have a mirror RAID setup. 2 160GB Lacie drives.

What would happen if one of them fails, whats the procedure for rescuing the other drive's data? Would the other drive be intact with its data and would it be easy to retrieve the data?

After setting up a mirror RAID. What would happen if I delete the set in Disk Utility? Will it format the drives or will they seperate from each other but retaining the same data I have stored on them?

Thanks.
 

pulsewidth947

macrumors 65816
Jan 25, 2005
1,106
2
To answer your first question, if one drive fails your computer should start using the other immediately. This is how it works on my PC using the same configuration, and I cant see how RAID would be different on a Mac.

As an educated guess I'd say if you delete the set from DiskUtil you'll probably have 2 seperate drives with identical data on. I couldnt say for definate though.
 

baummer

macrumors 6502a
Jan 18, 2005
951
27
Southern California
In theory, each drive would be identical to each other. If one drive were to crash, the other drive should still be fine and contain the same information as the first. Your next step would be to either repair or purchase a new drive to replace the failed drive. That's the whole point of a RAID setup.

Now, for your second set of questions, why on earth would you want to delete the set in Disk Utility??? :confused:
 

baummer

macrumors 6502a
Jan 18, 2005
951
27
Southern California
CrackedButter said:
Because I am curious to know what would happen.

Would the drives be formatted or would they each retain the information that has been backed up?
I've never tried this, nor have I ever had a desire to. I'm usually not in the habit of wanting to sabotage my drive setups. An educated guess would assume that if you delete them from the Disk Utility, that both drives would get the exact same treatment (again, the point of RAID).
 

Eniregnat

macrumors 68000
Jan 22, 2003
1,841
0
In your head.
Two types of failures require two different kinds of rebuild.

If it is a simple error, cataloging or for some reason a drive fell out of the RAID (usually due to a connection issue- but if it happens a lot, then the drive may be bad) then try the rebuild on disutility.

If not, you will have to rebuild the drives using terminal commands.
Apple has write ups:

Apple How To Rebuild a RAID Mirror
  • 1. Open the Terminal (/Applications/Utilities/).
  • Note: If you are started up from CD, you may open the Terminal by choosing it from the File menu. Also note that you should not precede any commands with "sudo" if you have gone into single-user mode.
  • 2. Type: sudo diskutil checkRAID
  • 3. Press Return.
    ...
[Read the original article]
Found by searching Apple Support.
http://search.info.apple.com/?search=Go&lr=lang_en&kword=&q=RAID failed
Technically, all this is doing is what disutility should allow you to do, but for some reason when it comes to RAIDS, the disutility doesn’t always allow for a simple and easy repair.

Other rebuild commands show up in the articles.

Now if in a mirror, you deleted one of the drives, it would be just like removing one of the drives, and the RAID should show as degraded, but usable. (Note: I work with NAS that run their own JAVA based operating system- so I am working from what I know.) When any one of my RAIDs is degraded, (and we run a mirror of our RAIDS-talk about the redundancy of redundancy). Basically, rebuilding the RAID at that point is a time consuming task... well it always is. I work with RAIDS of at least 4 drives with a hot auto-swapping 5th drive. Each NAS is also mirrored. I pity the person that has to rebuild a RAID. When one of our primary drives fails, it is a sucky day for me. If I didn't help any, then I at least bumped this up.

crackedButter I have always enjoied your posts. Why would you do this?
 

CrackedButter

macrumors 68040
Original poster
Jan 15, 2003
3,221
0
51st State of America
I don't want to do this! I simply wanted to know what would happen, I've never had a RAID setup before, so I'm only asking questions as to how things work. People are making a big deal out of this question!

Also when you setup a RAID for the first time, it asks to format your drives. Would it ask to format again if I replace a failed drive?