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[Bug-ddrescue] Recovering LaCie Raid Striped set

From: John
Subject: [Bug-ddrescue] Recovering LaCie Raid Striped set
Date: Sat, 26 Feb 2011 23:22:19 -0800
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv: Gecko/20101207 Lightning/1.0b2 Thunderbird/3.1.7

Recovering Raid Striped set.

Howdy All...

I have seen two emails regarding recovering RAIDs. There may be more/others-but I haven't seen them. I have raid recovery project I would like to take a stab at. This is for no other purpose but to learn so there really is no urgency or risk involved.

A friend gave me a LaCie drive and said it was a lost cause. She is using a Apple Intel machine. She said it was formatted to be the largest drive size so I take that to mean it was a stripe. It's two 500GB drives and she indicated it showed up as two drive but she followed LaCie's documentation to use Apple's Disk Utility and when she was done it showed up as one drive so is it safe to assume it's striped?

I was thinking that if I could recover both drives to .dmg files I could mount the DMGs and copy them back to two disks of the same size. I have recovered drives then repaired the restored images on fresh/new drives using D i s k W a r r i o r. So I would follow the same steps as a single drive.

I note that one email From Sebastian Sasu on [bug-ddrescue] mentioned "ddrescue did the trick, it managed to clone the drive onto another identical drive!!!! Of course the raid wasn't working, I had to reconfigure and rebuild, but without data loss!!!"

How is the reconfiguring and rebuilding done? Do I just create a new striped raid and add the two drives? Or is the some special process to doing this? In the case of the LaCie, I know they have a tool for formatting the drive but she said she used Mac OS X's drive utility to setup the raid. I don't know if LaCie's utility actually does any raid config but even it did, setting it up would be easy but how do I set it up with recovered data already on the drives? ...and do I repair with D.W. before or after?

Another email from Andrew Zajac said "you would need both drives to use the array (you need to assemble the array into one block device and then mount the filesystem on it)." What does "assemble the array into one block device" mean? How do I do this? And how do I "mount the file system on it"?

Andrew Zajac also said; "If not, you can always assign the partitions on the images to loop devices and then use mdadm to assemble the array using the loop devices (on Linux - don't know about OS X.)"

Does anyone know how to do this on Mac OS X? What are "Loop Devices?" And when using mdadm, what am I doing when I "
use mdadm to assemble the array using the loop devices?"

Please feel free to comment back to me and what ever information you can provide I would be very appreciative. If I can get enough comments and clarifications I will assemble it in a summary to the list.


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