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Could R8 Combed Media Set Be Confusing Diskwarrior?

Guest Cueballio

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Guest Cueballio

My main home computer setup these days is a Mac Mini Late 2009 with several WD My Book external drives, including two 4tb My Book Studio Edition II, each set up as Raid 0. One of the 4tb drives is now filled with a single Media Set, consisting of Retrospect backups of the other 4tb, and the much smaller internal startup volume and two smaller My Books. After perhaps 6 months, the Media Set had run out of room and began to comb the backup.


It seems that these My Book Raid drives have a major shortcoming...even though they supposedly are aimed at Macs (pre-formatted hfs+) their drives spin down to sleep and that cannot be overridden by System Prefs. So unless they are ejected before shutdown, there is a good chance that data sitting in the drive cache will be lost instead of getting written to disk. Too bad I didn't learn this until after I plunked down $1000 for the two. Drobos would have been a little more expensive, but...but...but I digress.


In the last week I had several system lockups requiring force-reboots, and sure enough, the working Studio II, which is the Retrospect source volume, became unmountable. My various drive utilites don't even see it. I will probably get a warranty replacement and restore from Retrospect.


I ran DiskWarrior on the other Studio II, which is dedicated to a single large media set and nothing else.

This is what DiskWarrior reported:


DiskWarrior has successfully built a new directory for the disk named "MB 4T 2." The new directory cannot replace

the original directory because of a disk malfunction.!


A disk malfunction is a failure of or damage to any mechanical component of the disk device, or any component

connected to it. The malfunction will likely worsen. Therefore, recovering your files from the DiskWarrior Preview as

quickly as possible is essential.!


t is highly recommended that you backup all of your data from the preview disk.!




All file and folder data was easily located.!


Comparison of the original and replacement directories could not be performed because the original directory was

too severely damaged. It is recommended that you preview the replacement directory.!


• Errors, if any, in the directory structure such as tree depth, header node, map nodes, node size, node counts, node

links, indexes and more have been repaired.!


Disk Information:!


Files: 7,206!

Folders: 20!

Free Space: 45.48 GB!

Format: Mac OS Extended (Journaled)!

Block Size: 4,096!

Disk Sectors: 7,813,353,744!

Media: WD!


Time: 5/2/11 9:36:14 AM!

DiskWarrior Version: 4.2 - RH284187



It could be that there is corruption damage to this drive as well, that isn't so severe that it prevents it from mounting...YET.


I wonder if there is another possibility...that the structure of this 4tb media set which has been combed at least a half-dozen times, looks like directory damage to DW causing a false alarm. I ran Disk Utility and Drive Genius on the drive, and neither saw a problem.


What are your thoughts on this? On any of this?? Thanks!

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that the structure of this 4tb media set which has been combed at least a half-dozen times, looks like directory damage to DW causing a false alarm


A Disk Media Set is just a folder full of files. There is nothing special about it that would cause DW to see it as something it is not.


That being said, it's really not wise to use RAID 0 to store your backup. Just as a twin engine airplane has twice the chance of loosing an engine as a single engine plane, your RAID 0 array has twice the chance of loosing one mechanism as a single drive volume. But while the airplane example can land on its remaining engine, the two disk array is forever toast if one of its disks dies.


With Retrospect, it would be smarter to use the device as JBOD, and have each drive act as a Member of the Media Set. Still the same odds of a drive failing, but if it does you still have a Member left (and the data it contains).

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Guest Steve Maser

Is Disk Warrior supposed to be able to scan 4TB drives? Maybe I'm thinking of an older version that does not...


Anyway, my 6TB external RAID drive (setup as Raid 5) has 8 media sets on it -- and I groom 3 of them every weekend (different ones frequently.) I have about 600TB left on the drive.


Every so often I scan it with Disk Utility and it has never reported any errors. I'm not sure if that helps as a data point or not.


But, I never have let the drive get to the point where it was so full it had to do a *force* groom, so I honestly don't know what happens to the structure when you run out of space.



But doing several "Force reboots"? That's probably what croaked the disk depending on what the disk was doing when you did that...

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