Unmounted External Hard Drive, Error: Filesystem verify or repair failed

I have had the exact same situation occur, but was able to follow these steps to successfully save everything!!

The Unix program "dd" will instruct a drive to stream out all of it's data from beginning to end without regard to file structure, therefore creating an exact block-for-block duplicate. By doing this, it will allow you to copy everything off without having to mount the drive. It also ignores any corruption or physically damaged blocks on the drive which would otherwise crash or freeze the Finder. It saves the data to a disk image file which you can then open and use without fear of imminent failure (the format of the disk image will be the same as the original drive). Now that the data is preserved, you can safely go through and recover your files. Keep in mind that if a file was damaged or corrupted on the drive, it will be unusable, but at least you'll be able to get to the good ones safely. In my case, using "dd", I had no problems and got every file off. If it doesn't work for you, at least it's impossible for just trying it to further damage your files. I can recommend a few other remedies if this doesn't work for you.

Note: The computer must be able to at least recognize the drive. That means either 1) It mounts 2) When you connect the drive the Finder asks if you want to erase or ignore, click ignore and you should be able to do this, or 3) Nothing happens in the Finder, but the volume in question does appear in Disk Utility. If you connect the drive and absolutely nothing happens and it never shows up in Disk Utility, it won't work.

Note: As always, it is suggested that you backup important data on your startup disk before proceeding with stuff like this. It is possible to wipe a drive by mistyping a terminal command, so double check before you hit enter.
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_Now, on with the show!_
Prep: Restart your machine so that it goes straight to the login window. Enter your user name and password. As soon as you press enter after your password, immediately hold down the shift key until the Finder finishes loading (this prevents any background startup items from running that might interfere).

1. Attach the drive to the computer and make sure you have another drive with enough free space to hold the entire capacity of the bad drive, not just it's used space, but the WHOLE size of the bad drive (for exception, see very bottom of this post).

2. In Terminal, type:
+diskutil list+
Look for the drive you want to recover in the "name" column, then write down it's "identifier" (ex. disk1s2)

3. In Terminal, type:
+dd bs=512 if=/dev/disk#s# of=/my_directory/image.dmg conv=noerror,sync+
!! Replace "disk#s#" with the identifier you wrote down before !!
!! Replace "/my_directory/" with the path to where you want to save !!
!! Replace "image.dmg" with the name you want to give the disk image (must end with .dmg) !!

4. To confirm that something is happening, open Activity Monitor (in the Utilities folder) and click "Disk Activity". Once you determine an average transfer rate, divide the size of the drive by that and then divide by 60 to see how many minutes it will take to finish. *+! ! FOR LARGE DRIVES THIS WILL TAKE A VERY LONG TIME ! !+* To be safe, do not use your computer for anything until the process finishes, you can leave Activity Monitor open so you can see when it's finished.

If you're only really concerned about a certain files and you know their exact path on the bad drive, let me know and I can give you modified instructions to copy just those files, saving the time and space of doing the whole drive.

Ryan,

Great walk-through. I have a Western Digital 160GB external hard drive that is behaving exactly like the other people's on this thread. I have a 4GB folder on the drive that I really need to salvage, and I was wondering if you could give me modified instructions on how to extract just that file. The hard drive was used for Time Machine, but its way to unreliable to be my primary backup drive. (Western Digital seems to have a habit of doing this, in my opinion.) If you could help me, I would really appreciate it.

Cheers, Chase

Chase,
If you are lucky enough that Disk Utility actually shows the correct name of the volume in it's sidebar and not just a generic name (although I guess you could try using whatever it uses), then the following adjustment should work:

In step #3 of my original post:
Replace:
/dev/disk#s#
With the full path to the file you want to recover. Example:
/Volumes/NameOfBadDrive/Users/Chase/Documents/importantfile.txt

NOTE: If some files you recover form this or the previous solution are still unusable, you can remove the word "sync" from the end of step 3. In Nick's case, it would not likely help as his drive works fine but stuff got scrambled. If a drive has hardware or bad block issues, removing sync will cause dd to try to read damaged or bad blocks over and over and over until it gets some data off it (sync tells dd to automatically write a zero when it finds damaged or bad blocks). In most cases it will eventually get what it needs and you therefore not have lost anything. This works great for scratched CDs and DVDs! HOWEVER... RUNNING WITHOUT SYNC CAN TAKE MANY TIMES LONGER.

Hi Ryan,

I had the same problem in that I unplugged my WD hard drive while it was running (I was in a hurry and forgot that it wasn't the printer cord!) and now that I try to plug it back in, the computer won't recognize it. My situation is different though in that I don't have anything on the HD that I really need. It was just my first time using time machine and backing up on it, and it was in the long, slow process of getting all my files backed up and stored. Did the thing destruct itself or what? Is there a simple way to just get it to start backing up again?

Thanks!
Kara

Hi Kara-
(In this answer I'm assuming you are okay with completely erasing the drive and loosing everything on it.)
The first step is to see how far gone the drive really is.
1. When you plug the drive into the Mac do any of these happen?
a. It asks if you want to initialize/ignore/eject/erase.
b. You can hear the hard drive spin up, but then nothing happens.
c. Nothing happens at all, the drive remains silent.

2. Regardless of the above; open Disk Utility in the Applications->Utilities folder, then plug in your drive. If nothing happens, you might let it sit for 5-10 minutes to see if anything pops up.
a. The drive shows up in the left hand column with it's correct name.
b. The drive shows up with some other name.
c. Nothing happens at all.

*What to do:*
1a. Press initialize or erase. You should be back to a normal empty drive.
1b. Move on to step 2 above.
1c. If it's under warranty, try contacting the manufacturer for a replacement. I wouldn't volunteer the story of how it happened, just that one day it stopped working.

2a. Since you're okay with erasing it, move to the next answer 2b to start fresh with the drive instead of attempting to recover it.
2b. Click on the drive once to highlight it. On the top part of the right hand window where it probably says FirstAid/Erase/RAID/Partition, make sure Erase is selected. In that window, next to "Volume Format:" select "Mac OS Extended (Journaled)" then enter a new name for your drive. Then press the Erase button. You should be back to a normal empty drive.
2c. Same as 1c.

*If in 2a or 2b it's greyed out and/or won't highlight when you click it, go to answer 2c.

I hope that helps! If something happens that I didn't mention, let me know.

Ryan,

I have a similar problem. Unfortunately, my computer will not boot to the login screen. I get the spinning wheel and then the computer shuts down. I can start the computer up in Target disk mode. Doing that I was able to copy the disk drive of my laptop to a WD external using my wifes iMac. However, the disk image would not mount. Any suggestions? I don't need to copy the entire drive, just my User folder. However, any other options you may provide would be most helpful. I've scoured the internet and this thread seems to be the most relevant to my situation.

Some Background.

Damaged drive is a 160GB HD on my Powerbook. WD external is a 250GB. Both of these drives were connected to my wife's iMac. The WD external mounts fine. The laptop will not mount even when booted in Target Disk mode. However, the laptop will properly start in Target disk mode and shows the Firewire symbol on the screen. I can boot up in single-user mode as well, if that helps.

Appreciate your help!

John

Hi John,
I'm guessing that you were able to create the disk image of the drive by using Disk Utility, meaning that although it won't mount, it does show up there. The image won't work because it has the same corrupted data that the drive does. What we'll do is go after the raw ones and zeroes data on the drive, ignoring the file structure. Since we're just trying to do your Users folder, you'll only need enough free space on the iMac or an external drive to hold that.

1. Restart the iMac so that it goes to the login window. Enter your user name and password. As soon as you press enter after your password, immediately hold down the shift key until the Finder finishes loading (this prevents any background startup items from running that might interfere).

2. Boot the PowerBook into Target Disk Mode. Then attach the PowerBook to the iMac.

3. In Terminal, enter this as one line:
+dd bs=512 if="/Volumes/XXX/Users" of="~/Desktop/YYY.dmg" conv=noerror,sync+
!! Replace "XXX" with the name of your PowerBook's drive (as shown in Disk Utility) !!
!! Replace "YYY" with the name you want to give the disk image !!

4. To confirm that something is happening, launch Activity Monitor (in the Utilities folder) and click the Disk Activity tab. Once you determine an average transfer rate, divide the size of the Users folder by that and then divide by 60 to see how many minutes it will take to finish. THIS CAN TAKE A LONG TIME! To be safe, do not use your computer for anything until the process finishes, you can leave Activity Monitor open so you can tell when it's finished.

OPTIONALLY: You can remove ",sync" from the command to improve the chances of recovering data. With sync, it will ignore bad or damaged blocks and just write a zero in those spots which can result in a few unusable files depending on the extent of the damage. Without sync it will attempt to read a bad or damaged block over and over and over until it thinks it has figured out what it should be which can result in 100% recovery, but it will take MUCH MUCH longer.

I'd love to know how it works out for you, so check back in afterwards!
-Ryan

Ryan,
Thanks for the quick response. I tried your suggestion but it did not work.

I used the following command (copied from Terminal):
dd bs=512 if="/Volumes/New Macintosh HD/Users" of="~/Desktop/OLDUser.dmg" conv=noerror,sync

Terminal responds with "
dd: /Volumes/New Macintosh HD/Users: No such file or directory

Some Notes:
Disk Uitility on the iMac can "see" the Powerbook's hard drive (the bad drive) but it will NOT mount. The command was executed with the bad drive not mounted.

Any other suggestions?

Thanks!
-John

Sorry, my mistake, that version of the command would only work if you could mount it.

Booted from the iMac, connect the PowerBook and launch Disk Utility. Select the PowerBook's drive in the left hand column. Click "Repair Disk" in the bottom right of the window.

(You could also just boot the PowerBook from the OS X install disc and select Disk Utility from the menu bar, but this is essentially the same thing.)

I have one last possible solution if this doesn't work, but it means working in Single User Mode which is a bit more complex. I won't have you do anything until I've tried it myself. Let me know if you'd like to go down that path.

Thanks Ryan. I've already tired repairing the disk using Disk Utility. It continuously fails with the same error message: "Keys out of Order." It then tells me it is repairing the catalog Btree and then fails stating "the disk could not be repaired. I've tried this using the iMac and the OS X CD, as well as using fsck in Single-User Mode. All fail with the same messages.

I'm comfortable using single user mode. I'm a newb at Unix but have a read a few books on Unix for Mac OS X. Would love to hear your single-user mode solution.

Thanks again for all of your help!
-John

I'm glad I read your post before I embarked on my journey to create the steps for my Single User Mode solution attempt! It wouldn't have worked in this situation.

I did a little searching and it seems like using DiskWarrior software is the most common solution to the "Keys out of Order" message. I try not to go straight to recommending third-party software for data recovery as I've been bitten in the past, but there are a lot of success stories from people in your situation. (I think I just need to get over what happened 9 years ago and accept that recovery software today is more stable than it was then.)

You'll find it at: http://www.alsoft.com/DiskWarrior
You can just get the download version and run it from the iMac with the PowerBook in target disk mode.