12 Replies Latest reply: Apr 20, 2010 11:49 AM by Ryan Androsoff
TheYodaMac Level 2 Level 2 (400 points)
I have 3 external 1.5TB FW800 drives.

2 were setup as a mirrored RAID using Disk Utility. One of those two now died.

Is it possible to add my extra 3rd disk into the RAID now to rebuild it? Disk Utility seems to only allow you to add additional drives when the RAID is fully functioning, not "degraded" as mine is now. (seems like that's exactly when you'd WANT to add another drive...)

Am I doing something wrong, or can I NOT add a drive to a "degraded" RAID in order to rebuild it up again?...

Suggestions?

 Intel MacMini , Mac OS X (10.6.3), TV  iPhone 3GS  "E-POD" (04' Honda Element)  "Mac" (my black cat)
  • Glenn Carter Level 4 Level 4 (3,360 points)
    Have you tried adding the spare drive to the RAID set?

    Adding a disk to a mirrored RAID set
    http://docs.info.apple.com/article.html?path=DiskUtility/11.5/en/7079.html
  • TheYodaMac Level 2 Level 2 (400 points)
    You would think that works. But it only seems to work when the RAID set is functioning, not in it's current "degraded" condition.
  • Glenn Carter Level 4 Level 4 (3,360 points)
    Just a shot in the dark, but what happens when you try to "Rebuild" the RAID set?
  • Glenn Carter Level 4 Level 4 (3,360 points)
    Have you tried using the RAID Utility found in your Utility folder?

    RAID Utility 1.0 Help If a Disk Fails
    http://docs.info.apple.com/article.html?path=RaidUtility/1.0/en/s1ru18.html

    Also, might this apply?

    "Tip: If you are adding a drive to be rebuilt into a degraded mirrored RAID set and the replacement drive used to be part of the same or another RAID set, it must be erased before it can be added to the mirrored RAID set." http://support.apple.com/kb/TA27188
  • TheYodaMac Level 2 Level 2 (400 points)
    I have it set to "auto-rebuild" - so the Rebuild button is greyed out. I can't click on it.
  • TheYodaMac Level 2 Level 2 (400 points)
    "RAID Utility is not supported on this computer." is the message it get when trying to use that program.

    And the 3rd drive I am trying to use has been erased.
  • Glenn Carter Level 4 Level 4 (3,360 points)
    Sorry, I'm getting the same dialog box as well. I guess it is only for Mac OS X Server.

    Then I don't have any other ideas. I was thinking of setting up a RAID with 3 or 4 drives as well using Disk Utility. But if you are having this much trouble then I might reconsider. I imagine you would have had better success with this if you had started out with more than 2 drives.
  • TheYodaMac Level 2 Level 2 (400 points)
    Really. So there is no way to add a new disk to a degraded RAID... that seems less than ideal.
  • Glenn Carter Level 4 Level 4 (3,360 points)
    I tend to agree with you. However, attempting to add a new disk to a "degraded" RAID that only consists of a single disk may be the issue here. If a single disk of a 3 or 4 disk RAID had died, then adding a new disk may have been achievable even in the RAIDs' "degraded" state. But the fact that the remaining RAID structure only consists of a single drive may be a hurdle that Disk Utility can't overcome. It's possible that the surviving data is not sufficient to rebuild the RAID as it existed prior to the failure and so it refuses to allow you to add another disk.

    This is merely speculation on my part. Perhaps one of our more experienced HD contributors (Kappy, baltwo, etc...) might pop in here are add some insight.
  • TheYodaMac Level 2 Level 2 (400 points)
    Well, as far as I can tell, all the data on the "surviving" drive is in perfect order.

    If nothing else, I can build a new RAID with two of the drives, then replace and add in the 3rd. I had been holding back the 3rd drive as a "spare", but once it's repaired I might as well use it that way.

    I was just hoping for a quicker fix for now, while waiting for a repaired 3rd drive.
  • Ryan Androsoff Level 2 Level 2 (390 points)
    Why don’t you delete the degraded RAID set (this should preserve the data on your source disk), create a new mirrored RAID set with ONLY the source disk in it (again, this should preserve the data on your source disk), and then add your third spare to this new “Online” RAID with 1 disk in it. Rebuild. Will this work?

    Pay attention to the warnings that pop up for each step - they should tell you that the data on your source disk will be unharmed.
  • Ryan Androsoff Level 2 Level 2 (390 points)
    Ryan Androsoff wrote:
    Why don’t you delete the degraded RAID set (this should preserve the data on your source disk), create a new mirrored RAID set with ONLY the source disk in it (again, this should preserve the data on your source disk), and then add your third spare to this new “Online” RAID with 1 disk in it. Rebuild. Will this work?

    Pay attention to the warnings that pop up for each step - they should tell you that the data on your source disk will be unharmed.


    I can confirm that this does work (I had to do it the other day to rescue my RAID), but should clarify terminology. At the first step, instead of deleting the RAID, you should “demote” the remaining good disk from the RAID, which would preserve its data and turn it into a regular disk (clicking the - button). You can then enable a new RAID by dragging that source disk back into the RAID tab and clicking “enable”. Basically just converting the normal disk back into a RAID disk. Data is preserved. You’ll now have an Online RAID with one disk in it. Perhaps you’ll be able to add that spare to the set now?

    This is a great article about all things RAID: http://www.afp548.com/article.php?story=appleraid2-in-depth