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Disk Utility RAID Question

5851 Views 12 Replies Latest reply: Apr 20, 2010 11:49 AM by Ryan Androsoff RSS
TheYodaMac Level 2 Level 2 (400 points)
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Apr 6, 2010 9:10 PM
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)
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    Apr 6, 2010 10:01 PM (in response to TheYodaMac)
    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
    MacBook Pro 2.4GHz (Early 2008), Mac OS X (10.6.2), MacBook Pro (2010-Any Minute), MacBook (2009), Time Capsule, AppleTV, 2 iPhones
  • Glenn Carter Level 4 Level 4 (3,360 points)
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    Apr 7, 2010 12:22 AM (in response to TheYodaMac)
    Just a shot in the dark, but what happens when you try to "Rebuild" the RAID set?
    MacBook Pro 2.4GHz (Early 2008), Mac OS X (10.6.2), MacBook Pro (2010-Any Minute), MacBook (2009), Time Capsule, AppleTV, 2 iPhones
  • Glenn Carter Level 4 Level 4 (3,360 points)
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    Apr 7, 2010 12:33 AM (in response to TheYodaMac)
    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
    MacBook Pro 2.4GHz (Early 2008), Mac OS X (10.6.2), MacBook Pro (2010-Any Minute), MacBook (2009), Time Capsule, AppleTV, 2 iPhones
  • Glenn Carter Level 4 Level 4 (3,360 points)
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    Apr 7, 2010 6:25 PM (in response to TheYodaMac)
    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.
    MacBook Pro 2.4GHz (Early 2008), Mac OS X (10.6.2), MacBook Pro (2010-Any Minute), MacBook (2009), Time Capsule, AppleTV, 2 iPhones
  • Glenn Carter Level 4 Level 4 (3,360 points)
    Currently Being Moderated
    Apr 9, 2010 2:43 PM (in response to TheYodaMac)
    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.
    MacBook Pro 2.4GHz (Early 2008), Mac OS X (10.6.2), MacBook Pro (2010-Any Minute), MacBook (2009), Time Capsule, AppleTV, 2 iPhones
  • Ryan Androsoff Calculating status...
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    Apr 17, 2010 12:55 PM (in response to TheYodaMac)
    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.
    MacBook Pro 4,1 (15-inch) (2.5gH, 4 GB RAM, 500GB), Mac OS X (10.6.2), iphone 3G 16gig 3.1.2
  • Ryan Androsoff Level 2 Level 2 (390 points)
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    Apr 20, 2010 11:49 AM (in response to Ryan Androsoff)
    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
    MacBook Pro 4,1 (15-inch) (2.5gH, 4 GB RAM, 500GB), Mac OS X (10.6.3), iphone 3G 16gig 3.1.2

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