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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Broken RAID 1 Mirror

I have uncovered today that my RAID 1 10.4.11 G5 server has had the mirror break sometime before or when I did the the upgrade from 10.4.10 to 10.4.11. I've been looking around, and I can't seem to find direction on how to properly 'break' the mirror.

I'd like to 'break' the mirror so I have 1 good drive, then clone the drive, and re-establish the mirror. Can someone point me in the direction of some documentation or guide me through that process?

At the moment I'm scarfing up a copy of the data so if 'really bad things' happen, we'll not be waiting too long to restore and repair things. It's always good to have an 'extra' copy of your backup!

Thanks for the help!

MacBook Pro 15" 2.53 GHz Intel Core 2 Duo, Mac OS X (10.5.6), 4G RAM

Posted on Apr 7, 2009 3:41 PM

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14 replies
User profile for user: Antonio Rocco
Antonio Rocco
User level: Level 6
12,278 points

Apr 10, 2009 8:09 AM in response to Lionchild

Hi

A RAID is not a backup. All it provides is a measure of redundancy and fault-tolerance. There's enough documentation regarding what to do using either the command line or Disk Utility itself. In Terminal issue man diskutil. Selecting 'Disk Utility Help' after launching Disk Utility should give further options. Select 'Using RAID sets > mirrored RAID, further options from there.

Before going any further it's advisable you make a current and effective backup.

Tony
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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Apr 10, 2009 9:32 AM in response to Antonio Rocco

Tony -

Trust me, the first thing I did was make extra backups.

I did uncover this article from another group via the MacOSXTiger section of Apple Support:

http://discussions.apple.com/thread.jspa?threadID=957124&tstart=0

I just picked up a pair of 1.5Tb drives to replace the 500Gb drives with. I've built a 'clean' OS X Server 10.4.11 install on a 40Gb HD that I'm going to clone over to one of the 1.5Tb drives. I'm then going to copy current, valid data to the new 1.5Tb drive, then clone that to the second 1.5Tb drive.

That brings me back to the big question: For redundancy, how do I thus reset my RAID 1 mirror in place once I've cloned the drives to be identical? Or, do I just make the one operational drive, then setup a mirror via Disk Utility and let it do the cloning?
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User profile for user: Antonio Rocco
Antonio Rocco
User level: Level 6
12,278 points

Apr 10, 2009 9:54 AM in response to Lionchild

Hi

The way I would do this would be to remove the internal RAID 1 Set (both drives). I'm guessing the current RAID set contains everything? OS and Data? Install one of them in an external drive case. They're cheap enough and besides are a useful thing to have.

Install the replacement drives. Connect the external drive case (should be firewire). Boot from any installer disk that will boot the hardware being used. Launch Disk Utility from the appropriate Menu. Partition the two new drives. Create a RAID 1 Mirror Set. Make sure you select the 'Automatically rebuild RAID' option. Leave everything else at their defaults. Use Disk Utility to restore the external drive (as the source) to the newly created RAID Set (as the destination). This will take some time as data is written to both drives. When done set the internal RAID set as the Startup Disk. Restart and disconnect the external drive. Remove the drive from the external drive case and place it with the other drive. Put these away and keep them safe for a short while just in case.

Out of curiosity does the hardware/OS support booting from 1.5TB drives? I'm guessing it does otherwise you would not have bought them?

Tony
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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Apr 10, 2009 5:18 PM in response to Antonio Rocco

Tony -

I have 1 of the 1.5Tb drives installed now with a fresh copy of the OS installed. I don't want to just clone the working HD, because it seems ...flakey. I think there's something going on that I want to get rid of with a fresh install. I haven't finished the first copy, but I'll soon find out if the 1.5Tb drive will boot the OS. It seems to see data on it just fine.

I'll have an update later today or tomorrow with the status of the new drive. After the copy, I'll swap out and then add the 2nd 1.5TB drive to use in the mirror. I'll keep the old 500GB HD as a backup copy of the current data as of COB today.
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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Apr 10, 2009 6:23 PM in response to Antonio Rocco

Tony -

The 2 x 1.5TB HD's are installed internally and have a running OS X Server on them. However, I don't have a successful mirror. In order to do that, it would appear that I need to do it before I install the Server OS.

I'd like to run a mirrored set, I think. But, at this stage, I'll settle for a stable OS the users can use and then find a way to schedule backups to the other 1.5TB HD on a nightly basis. I'm open to suggestions on how to take Server 10.4.11 into a mirrored configuration without having to re-build the OS from scratch.
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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Apr 11, 2009 7:31 AM in response to TheYodaMac

Yoda -

I think when you build the mirrored RAID the first time, you need to go into the Options section and check the box to automatically rebuild the RAID. That may have been something that was missed when I first created this system several years ago. I'm not sure under 10.4.11 what the proper proceedure is to rebuild things, aside from starting from scratch, then copying your data back onto the new setup. 😟

As of now, I've simply rebuilt from scratch with a pair of drives in a non RAID 1 mirror, and will be using 3rd party utility to make nightly backups to changes in the data on the volume so that I'll have a ready-to-use backup copy.
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User profile for user: TheYodaMac
TheYodaMac
User level: Level 2
400 points

Apr 11, 2009 11:05 AM in response to Lionchild

Yes, I actually did choose to auto-rebuild the RAID when I originally created it, and as the bad drive began failing - it kept rebuilding and restoring the data to that drive each time. (which is great, and what it was supposed to do)

Now that the bad drive has been repaired and returned - I am trying to figure out the steps I need to take to "put it back" into the RAID again. It just shows up on the desktop as another external drive.
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User profile for user: Lionchild
Lionchild Author
User level: Level 1
94 points

Apr 11, 2009 8:22 PM in response to TheYodaMac

Yoda -

After you re-installed the replacement drive, it didn't try to auto-rebuild?

So far, I've been a little underwhelmed with the mirroring for 10.4.11. I suspect 10.5.x has this little issue 'fixed' in it. It would be nice if Apple might chime in and answer the question. You're having this issue on a Mac Pro and not actually an XServe, aren't you?
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User profile for user: TheYodaMac
TheYodaMac
User level: Level 2
400 points

Apr 11, 2009 8:45 PM in response to Lionchild

Actually I'm using a Mac Mini with 10.5.6, and two external USB2 Hard Drives for the RAID for storing my media.

It didn't automatically start rebuilding. Not sure if it's because a part (the bridge board - whatever that is) was replaced in the old hard drive and now it "sees it" as a new drive.

The Disk Utilities help makes it sound like all I have to do is highlight my RAID, then drag the "new" disk into it and click rebuild to add that disk.

You do get a warning message saying:

"Rebuilding a RAID set will destroy all information on the replacement disk “ST375064 0A Media”.
Are you sure you wish to rebuild the RAID set “MEDIA”?"




UPDATE: Okay, I did as described above and it seems to be working fine - rebuilding the new drive and leaving the existing one alone. (whew!). My RAID still shows as "degraded" - but I am hoping that will go away once the 2nd drive is done. I'll know in 12 hours....

Message was edited by: TheYodaMac
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Broken RAID 1 Mirror

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