Disk Utility: "Repairing disk failed with error Could not unmount disk"

Disk Utility: “Repairing disk failed with error Could not unmount disk”
Hi. I’ve been experiencing some mildly squirrelly behaviour with my system (vide infra) so decided to repair the two internal hard drives on my computer. The primary hard drive is a 74.53 GB ST380013AS that came with the system; its S.M.A.R.T. Status is “verified” and Disk Utility repairs permissions just fine. However, the second internal drive (Maxtor 6L250S0, 233.76 GB, lower Bay, Journaled HFS+), despite being verified by S.M.A.R.T. status and apparently running OK, fails to unmount when I ask Disk Utility to repair it- I get the above error message in red. I have repaired this disk with DiskWarrior (v3.03) and all appears to run AOK. Can anyone tell me why I cannot get Disk Utility to run on this secondary (eg, non-startup) disk? I have tried many times and the error is reproducible. Thank you!
G5 1.6GHz PPC, 1 GB RAM, running OS 10.4.6

Thank you for these useful links!
For others who have this issue, I also found very helpful advice given to this question on the MacFixIt forums by MicroMat Tech3 at
http://www.macfixitforums.com/php/showthreaded.php?Cat=&Board=tiger&Number=76265 1
He said: "Use the lsof command to find the open files on a volume that does not unmount or eject. Open Terminal, located in /Applications/Utilities. Type: sudo lsof | grep Leave a space after the p in grep, then drag the icon of the problem volume to the Terminal window. The pathname for the volume is pasted in for you; press Return. Then enter your administrative password at the prompt, and press Return."
At this point, one now has a list of the open files/processes on the volume that will not unmount. You can use Activity Monitor to terminate these processes if you wish, and then the volume will unmount as it should.

Similar Messages

Verify volume failed with error Could not unmount disk!!

Im having weird things with my fw lacie 200gb. I come across these weird white cubes which pop up in the search mode in finder. So i tried to repair permissions of the Lacie disc and i get this sign
Verify volume failed with error Could not unmount disk
What is this?
What are those white cubes in the finder?

Hi gizeh12!
Are you able to verify the volume of the disc (not permissions)? It could possibly be some bad/corrupt sectors on the drive. Is it a white box with a dashed line outline? Does the file size show the accurate value in "Get Info" when you click on the file?
Are those files somewhere else as well?

External hard drive reformatting error: 'could not unmount disk'

I've bought a TrekStor DataStation maxi light 2TB external harddrive and I am trying to reformat it so I can use it with my Mac.
Unfortunately when I try to either 'Erase' or create a partition as detailed here: https://discussions.apple.com/thread/2701878?start=0&tstart=0 I get the 'could not unmount disk' error.
Is anybody able to offer a solution?
Kind regards,
Rhyno

Sounds like something is using (or trying to use) the disk.
Eject it if you can. Then unplug and reconnect, and try again.
If all else fails, you may have to power down, start up from your Snow Leopard Install disc and erase/format it from there. See the yellow box in #6 of Using Disk Utility.

Error: Could not unmount disk

Hi: I am having a problem with an external HD (WD 750 GB Caviar Black) housed in an OWC enclosure and attached to my PowerPC G5 running OS X 10.4.11. The only use the drive has seen is trying to create a clone of my primary HD onto a partition on the external using a highly respected application dedicated to this purpose. For some reason yet uncovered, every cloning attempt has stalled the application and hung up my system. That aside, what is happening now is that I cannot even leave the ext. HD powered on and attached to my G5 as within minutes of booting up, my system slows down and becomes unresponsive. Detaching the ext. HD frees my system up instantly.
The last time I ran Disk Utility on the external, it passed verification and I was even able to run DiskWarrior on it and restore the directories to perfect order. But now, even after booting up from my original Mac install disk, although the external shows up in Disk Utility and I'm able to verify it just once (and it passes), any attempt after that to erase it, repartition it, verify it again, results in the error message: Could not unmount disk. Eventually I get the spinning beach ball and have to detach the drive. The drive does not make any unusual sounds and I have to put my ear to it to hear it at all. At one point, on boot up, the blue light on the enclosure continued to flicker for a very, very long time and the drive refused to mount altogether. But it hasn't done that again. I've read that when a drive won't unmount, it can mean that there are open files on it.
Anyone have any ideas as to whether it sounds like a problem with the enclosure or the drive and any suggestions as to what I might try? I have tried connecting it via eSATA, FireWire and USB (all from the same enclosure) and the results are the same.
Jack

Here's an update. Received the new enclosure. Before I transferred the drive into it, I unplugged the internal cables from the old enclosure that were connected to the drive and then reattached them. Also, I noticed that one of the cable plugs was not perfectly seated on the circuit board, so I pushed that in a bit. Heard a tiny click.
Using the old enclosure, the drive mounted quickly and I was able to Zero Data on it and erase it using Disk Utility. Was not able to Zero Data on it before. Would hang every time.
Thought I would try a different cloning app than the one I had been trying to use and this time the transfer did not stall. The estimated time, however, was about 6 1/2 hours which I thought was way too long to transfer 190GB via FireWire 800. The transfer rate started at 4.5MB/sec and went up to 9.5MB/sec. So I thought I would try the new enclosure and see if that was faster. I stopped the operation, erased the partition and transferred the drive to the new enclosure.
Tried the same cloning app that worked in the old enclosure and this time it stalled shortly after starting to copy files. Erased the drive and tried the original cloning app that had stalled using the old enclosure. It stalled using the new enclosure also. Erased the drive and tried the Restore function in Disk Utility and that went through. Took 4 hours. Attempted to boot up from the backup that Disk Utility created but I got the circle with the diagonal through it and it just hung there, with my fans running at top speed. Finally had to power down manually.
I'm thinking maybe it's the drive that's malfunctioning. It is still under warranty. Even though I'm not able to boot from the backup partition Disk Utility created, I'm wondering why it was able to transfer 190GB of data when the other two, well respected cloning applications stalled.

Ebs 11i Cloning in Win 2003 dbtier fails with ERROR: Could not open

Hi,
The rapidclone - DBTier cloning (11i) on Windows 2003 server fails with the following weird error message.
There is no detailed log file created.
echo %PATH%
f:\oracle\prodora\8.0.6\bin;f:\oracle\proddb\9.2.0\apache\perl\perl\5.0053\bin\mswin32-x86;D:\mksnt\mksnt;;
F:\oracle\proddb\9.2.0\appsutil\clone\bin\> perl adcfgclone.pl dbTier
Enter the APPS password [APPS] :
apps
First Creating a new context file for the cloned system.
This program is going to ask you information about the new system:
ERROR: Could not open
Any inputs on this really appreciated.
Thanks,
Prasanna

which perl picks up from the path f:\oracle\proddb\9.2.0\apache\perl\5.00503\bin\mswin32-x86/perl.exe.
Please check the below messages.
I had verified adchkutl.sh script too (not sure whether this will be invoked in windows env) ?
F:\oracle\prodappl\ad\11.5.0\bin>which perl
f:\oracle\proddb\9.2.0\apache\perl\5.00503\bin\mswin32-x86/perl.exe
F:\oracle\prodappl\ad\11.5.0\bin>adchkutl.sh
Checking for make... found - D:\mksnt\mksnt/make.exe
Checking for ld...
Unable to locate 'ld' utility in path
Checking for cc...
Unable to locate 'cc' utility in path
Checking for ar...
Unable to locate 'ar' utility in path
Unable to locate all utilities with system path.
PATH = f:\oracle\proddb\9.2.0pache\perl?.0050in\mswin32-x86;D:\mksnt\mksnt;;
F:\oracle\prodappl\ad\11.5.0\bin>which ld
D:\mksnt\mksnt/ld.exe
F:\oracle\prodappl\ad\11.5.0\bin>which cc
D:\mksnt\mksnt/cc.exe
F:\oracle\prodappl\ad\11.5.0\bin>which ar
D:\mksnt\mksnt/ar.exe
F:\oracle\prodappl\ad\11.5.0\bin>
Thanks

Please Help, After Kernel panic restart failed- apple swirl(6 hrs), SafeMode-failed, SUMode-sucess. Could not unmount disk to erase. Repair permissions-multiple fail errors:unable to set permissions on... unable to set owner and group...

Please Help, I deleted an account that was the same name as the administrator but was not the administrator. Also a samsung galaxy s phone was charging through the usb port.
I closed out a program and got a message that the temp file could not be stored/saved.
Then a Kernel panic message occurred and restart was necessary.
The restart resulted in the screen with the apple logo and a continous swirl for 6+hrs,
Attempted Safe Mode start up, unsuccessful,
Single User Mode-sucess.
Ran $ fsck_hfs -rfd /dev/disk0s2 Ran several times repairs made with one which remained. something about a node.
No change in start up attempts
Started with install CD matching current OS 10.6
Ran Disk Utility Repair Permissions resulting in multiple errors:
One line/error
Warning: SUID file /////Ardagent has been modified and will not be repaired
144 lines/errors of this type of series of lines
Group permissions differ on...should be drwxr-xr-x, they are -rw-r--r-- .
permissions differ on...should be drwxr-xr-x, they are -rw-r--r-- .
unable to set owner and group...error 22: Invalid Argument
unable to set permissions on...error 22: Invalid Argument
Ran Repair Disk, result:
Error: Could not unmount disk (in red)
Ran Verify Disk, result:
The volume HD appears to be ok (in green)
Next I attempted to erase the dist to start from scratch since I have data backed up on time machine.
Error message box
Volume Erase failed
Volume Erase failed with error:
Could not unmount disk
I am looking to solve without buying DiskWarrior unless only resort.

So it looks like solved it for now I will update later. What I did was after starting from the install cd for the 10.6 system I ran from terminal ran:
diskutil disablejournaling /dev/disk0s2
diskutil disableownership /dev/disk0s2
diskutil repairPermissions /dev/disk0s2
then i closed terminal and then when to disk utility and chose to repair disk with results all was fine. Then ran repair permissions and got similar results from terminal function next I erased disk and then chose to restore from time machine and it is now restoring! yea!

Could not unmount disk (-10000)

Hello all.
Just a quick one...
Just tried to verify/repair my External LACIE using Disk Utility, and found that I get this error...
Repairing disk for “LACIE HD”
Repair attempted on 1 volume
0 HFS volumes repaired
1 volume could not be repaired
Repairing disk failed with error Could not unmount disk (-10000)
Any ideas why this would happen? I have used Disk Utility before to Verify my External Drive...?! Any help would be much appreciated.
Kind Regards.
Jamesy!

Application Scripting Errors
-10000 Apple event handler failed.
Apple Event Registry Errors
-10000 AppleEvent handler failed.
Click a pic to feel the awesome 30" • Clone your boot drive, read my how to post here

Disk Utility, 'Could not unmount disk'

In what state - if any - does Disk Utility leave a Disk or Volume when I get the 'popup' error, "Could not unmount disk"?
I've had this on a variety of SATA and Firewire 400 disks under Tiger; typically, repeating the process in question (a Repair, Erase or Partition) seems usually to be successful, eg:
Creating Partition Map
Partition failed for disk Maxtor 7L250S0 Could not unmount disk
Partition complete.
(That's from DU's log; to me it's contradictory.)
But it looks as though something is set somewhere as a result of the apparent failure and as though there is a knock-on effect for such cloning s/w as the excellent SuperDuper!
I have ruled out hardware and experienced this 'error' with three different drives from two different manufacturers.
Is some bit or similar set somewhere which marks the drive as unmountable to the OS and third party apps, even though it is always subsequently usable in the Finder?
TIA!
G5 DP 2 GHz Mac OS X (10.4.3) clean machine; no haxies, perms repaired; lots of space etc!

Turned out to be a corrupt loginwindow.plist preference. Solved

Is my HD Dead? Reformat Disk Utility Error: secure disk erase failed with the error could not open disk.

Hi,
Fed up with seeing the spinning beach ball I decided to reformat my MacBook Pro...
After backing up everything on an external hard drive I put in the OSX install DVD, restarted the machine and held down 'C'.
I followed the install prcedure, clicking next a few times etc...
I then went into Utilities > Disk Utility. I chose 7-Pass to erase the Macintosh HD and set it off erasing.
I checked the process an hour in and message on screen read:
Secure disk erase failed with the error:
could not open disk
The internal hard drive no longer exists in the disk utility so I cant retry erasing it.
The only thing that appears in disk utility is the OSX install DVD.
I can't even shut down the mac as everything under the apple tab is greyed out!
I'm guessing this means my hard drive is broken right?
If anyone has any other ideas of what to try I'd really appreciate that.
How do I turn the machine off?
If my hard drive is gone then should I consider getting an SSD drive?
Any recommendations for such a drive would be great.
Hope you can help!

Did you partition the drive?
Extended Hard Drive Preparation
1. Open Disk Utility in your Utilities folder. If you need to reformat your startup volume, then you must boot from your OS X Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger or Leopard.)
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.
3. Click on the Options button, set the partition scheme to GUID (only required for Intel Macs) then click on the OK button. Set the number of partitions from the dropdown menu (use 1 partition unless you wish to make more.) Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the volume(s) mount on the Desktop.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
Steps 4-6 are optional but should be used on a drive that has never been formatted before, if the format type is not Mac OS Extended, if the partition scheme has been changed, or if a different operating system (not OS X) has been installed on the drive.

Backups failing with error 19: the backup disk could not be resolved, or there was a problem mounting it

Hello all,
Doubt this issue relates to a recent and ugly issue but sharing anyways (resolved thanks to a user here: LaPastenague)
Time Capsule won't backup if Modem (Motorola SB6121) attached
This was on Feb 10th resolved. Few days later I upgraded to Yosemite. Backups were working fine since.
Yesterday I happen to notice my last backup was 5 days ago. I looked in the console logs and saw:
2/25/15 3:55:06.127 PM com.apple.backupd[2777]: Attempting to mount network destination URL: afp://Paul;AUTH=SRP@Time%20Capsule._afpovertcp._tcp.local./Data
2/25/15 3:55:17.778 PM com.apple.backupd[2777]: NAConnectToServerSync failed with error: 2 (No such file or directory) for url: afp://Paul;AUTH=SRP@Time%20Capsule._afpovertcp._tcp.local./Data
2/25/15 3:55:17.792 PM com.apple.backupd[2777]: Backup failed with error 19: The backup disk could not be resolved, or there was a problem mounting it.
2/25/15 3:57:18.808 PM com.apple.prefs.backup.remoteservice[2021]: Attempt to use XPC with a MachService that has HideUntilCheckIn set. This will result in unpredictable behavior: com.apple.backupd.status.xpc
I called Apple. Their front line was clueless. He suggested resetting the TC (latest "tower" model btw") which then a backup kicked off YEAH
But the next hour it failed
Called Apple again, this time to Sr Advisor. He suggested factory reset of the TC and set up again. Also first backup worked then rest failed
Third call to Apple useless also. He was asking questions I didn't feel relevant. He also was asking me to reset the TC which I told him was done 2 hours prior. He asked me to reboot which I could NOT at that time.
I begged him to collect data to submit to engineering, which will take days to get a reply.
So I thought I would throw this out to the community....
TC Is NEW (replaced from last issue). Mac is 8 months old (iMac 27"), Os is Yosemite, TC also new (latest model)
Thanks...

Yosemite is problematic on two fronts.. Networking and Time Machine.. so the combo of doing both with a Time Capsule is like bugs on bugs.
Here is my standard list.. but your problem maybe difficult to resolve.. and my suggestion is simple.. until Apple get their act together and fix TM.. buy Carbon Copy Cloner and use that for your backup. It is solid and reliable.. even better if you use USB drive plugged into the computer and do a bootable clone.. because then you have a backup that is able to be tested for full functionality 2min after the end of the backup.
This also starts from a factory reset.. but the reason for it is to change the configuration which is much more easily handled with factory reset to begin.. the instructions are there.. because this is my standard reply.. this is not uncommon!!
Factory reset universal
Power off the TC.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the TC to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.
N.B. None of your files on the hard disk of the TC are deleted.. this simply clears out the router settings of the TC.
Setup the TC again.
ie Start from a factory reset. No files are lost on the hard disk doing this.
Then redo the setup from the computer with Yosemite.
1. Use very short names.. NOT APPLE RECOMMENDED names. No spaces and pure alphanumerics.
eg TCgen5 and TCwifi for basestation and wireless respectively.
Even better if the issue is more wireless use TC24ghz and TC5ghz with fixed channels as this also seems to help stop the nonsense. But this can be tried in the second round.
2. Use all passwords that also comply but can be a bit longer. ie 8-20 characters mixed case and numbers.. no non-alphanumerics.
3. Ensure the TC always takes the same IP address.. you will need to do this on the main router using dhcp reservation.. or a bit more complex setup using static IP in the TC. But this is important.. having IP drift all over the place when Yosemite cannot remember its own name for 5 min after a reboot makes for poor networking. If the TC is main router it will not be an issue.
4. Check your share name on the computer is not changing.. make sure it also complies with the above.. short no spaces and pure alphanumeric.. but this change will mess up your TM backup.. so be prepared to do a new full backup. Sorry.. keep this one for second round if you want to avoid a new backup.
5. Mount the TC disk in the computer manually.
In Finder, Go, Connect to server from the top menu,
Type in SMB://192.168.0.254 (or whatever the TC ip is which you have now made static. As a router by default it is 10.0.1.1 and I encourage people to stick with that unless you know what you are doing).
You can use name.. SMB://TCgen5.local where you replace TCgen5 with your TC name.. local is the default domain of the TC and doesn't change.
However names are not so easy as IP address.. nor as reliable. At least not in Yosemite they aren't. The domain can also be an issue if you are not plugged or wireless directly to the TC.
6. Make sure IPv6 is set to link-local only in the computer. For example wireless open the network preferences, wireless and advanced / TCP/IP.. and fix the IPv6. to link-local only.
There is a lot more jiggery pokery you can try but the above is a good start.. if you find it still unreliable.. don't be surprised.
You might need to do some more work on the Mac itself. eg Reset the PRAM.. has helped some people. Clean install of the OS is also helpful if you upgrade installed.
Tell us how you go.
Someone posted a solution.. See this thread.
Macbook can't find Time Capsule anymore
Start from the bottom and work up.. What I list here is good network practice changes but I have avoided Yosemites bug heaven.
This user has had success and a few others as well.
RáNdÓm GéÉzÁ
Yosemite has serious DNS bug in the networking application.. here is the lets say more arcane method of fixing it by doing a network transplant from mavericks.
http://arstechnica.com/apple/2015/01/why-dns-in-os-x-10-10-is-broken-and-what-yo u-can-do-to-fix-it/

Disk Utility Error Message for Firewire HD: Could not unmount disk

I have one internal HD with 10.4.2, another with 9.2.2, and an external firewire with 9.2.2. Sometimes the firewire does not show up on my desktop, or when I try to copy files onto it the beachball spins endlessly. When I try to reboot holding down the Option key, the firewire HD does not show up.
I ran TechTools 4.05 (while booted from my Tiger HD) on the firewire HD. Everything checked out.
I tried running Disk Utility on the firewire. The first time this is what I got:
"First aid failed. Invalid key check. Volume check failed. Error: The underlying task reported failure on exit."
I ran Disk Utility again:
"Repairing disk failed with error. Could not unmount disk."
Any suggestions would be appreciated.

Your firewire disk is damaged. Try that: restart in safe mode (pressing SHIFT after the chime). Wait for complete boot. Plug the external HDD. Try again with Disk Utilities. Wait the report. My advise is to check its integrity. Try repair. If nothing works, try with DiskWarrior (the best utility).
If DiskWarrior can't do the job, you – definitely have a damaged hard disk.

Error during Tiger install, disk utility (DVD) says could not unmount disk

OK, I'll start at the beginning. I was running 10.3.9 on my iMac G4. I hooked up a new firewire external HD. Transferred my iTunes music over, everything worked fine. Ran software update to make some updates (iTunes, Quicktime, Security Update, maybe another one) that I had been putting off because I had been out of space. That's when the problems began. It said I could not install updates, so I restarted. Then it hung up at Login Window starting. I did a few hard shutdowns (holding down power button) to try again, but was unsuccessful.
Read all the forums. Decided that I should have repaired permissions, etc. before installing the updates. So I started in single-user mode, ran FSCK, all that stuff, following the instructions very closely. Still kept hanging up at Login Window. So I started up from the Panther install disk, repaired permissions (made a bunch of repairs) and checked hard drive (said no repairs necessary). Restarted, still hung up at Login Window starting.
So I did an archive and install. There were errors near the end of the Panther install, and it said it could not finish. But the computer started up OK, and I was able to back up all my personal data onto the external HD.
So I decided to upgrade to Tiger, thinking that would fix everything. During the upgrade, it said there were errors installing files and to try again. Did so, same result. The computer did start up in Tiger, but clearly was not operating at full capacity (slow, some things didn't work).
So I decided to erase and install. Again, said there were errors and to try again. Did so twice, same result. Started up from the Tiger DVD and ran Disk Utility. When I clicked Repair Hard Drive, it said "could not unmount drive."
So now I am stuck. I have a wiped hard drive. Can't repair it, and can't get Tiger to install properly. Help!
(i do have an Apple store in town, but I haven't gone to the Genius Bar. Wasn't sure how that worked.)
iMac G4 Mac OS X (10.4.6)

Hmmm. And you're sure that when you select the main
hard drive entry in Disk Utility it shows a SMART
status report that says "Not supported"? That's
really odd because your model isn't too old to have a
drive that doesn't support SMART.
Yep, looking at it right now. I've got the drive that says "38.2 GB ST3408..." selected, and it says "Not Supported."
By any chance would you have another external
Firewire drive on which you could install Tiger? If
you do, then you could try installing Tiger on that
drive. If you can then boot the iMac from the
external drive you could then try cloning the system
from the external drive to the internal drive.
I have the one external HD firewire drive. It has my backed up files on it. Could I still install Tiger on it without erasing those files?
You could do the same thing from another Mac if both
support Firewire. You could boot the iMac into Target Disk Mode while it's connected to
another Mac's Firewire port. You could then clone
from the other Mac to the iMac's hard drive that will
appear on the Desktop of the other Mac.
And I do have another Mac, which I am typing on right now. It's sitting right next to my "sick" iMac. If I recall correctly, it's an iMac DV special edition. It does have a firewire port and I think it has a DVD drive. It's running 9.0 currently.
You can use the Restore option of Disk Utility to do
the cloning. The process is as follows:
1. Open Disk Utility from the Utilities folder.
2. Select the source or startup volume from the left
side list.
3. Click on the Restore tab in the DU main window.
4. Drag the source or startup volume to the Source
entry field.
5. Select the destination or backup volume from the
leftside list and drag it to the Destination entry
field.
6. Check the box to Erase Destination. Skip this
step if you've already formatted the drive.
7. Double-check you got it right, then click on the
Restore button.
So should I use the firewire external HD or the old iMac to do this? (Thanks so, so much for all this help, by the way. I really appreciate it. I love my iMac and want to save it! I have to go cook dinner right now, but I'll come back later to check your answer and try your suggestion.)

Partition Failed -- Could not unmount disk

I partitioned my external hard drive into two parts. Now I want to change it back to one partition (500 gb).
I backed up all the data.
When I use disk utility and try to re-partition to create one partition from the two existing partitions, I get the error message:
Partition failed
Could not unmount disk.
What am I doing wrong??
THANKS.

Sean M wrote:
I partitioned my external hard drive into two parts. Now I want to change it back to one partition (500 gb).
I backed up all the data.
When I use disk utility and try to re-partition to create one partition from the two existing partitions, I get the error message:
Partition failed
Could not unmount disk.
What are you booting from Sean ?
You could always startup with the external Off, runn DU then turn external ON.. and try.

Volume erase failed could not unmount disk

I have a Mac book Pro running 10.5.8 OSX. I'm trying to use Time Machine (need to replace the hard drive), and I bought a 1TB Toshiba portable hard drive. I read the instructions on the drive, which say that to use Time Machine, I'll need to reformat the drive as an HFS+. I found instructions to do that through Disk Utility --> Erase, with selecting Mac OS Extended from the Volume Format option. However, I keep getting the following message: "Volume erase failed. Could not unmount disk." I'm new to most of this, and have no idea what unmounting the disk is, much less how to resolve this. I found a thread that said to check my computer's name, which I did, but that didn't seem to help.

Likely where that second "Drive" came from, but may be gone now...
In Finder's Menu, select Go menu>Go to Folder, and go to "/volumes". (no quotes)
Volumes is where an alias to your hard drive ("/" at boot) is placed at startup, and where all the "mount points" for auxiliary drives are created for you to access them. This folder is normally hidden from view.
Drives with an extra 1 on the end have a side-effect of mounting a drive with the same name as the system already think exists. Try trashing the duplicates with a 1 or 2 if there are no real files in them, and reboot.
If it does contain data...
http://support.apple.com/kb/TS2474

Could not unmount disk

I am trying to do a clean install from Snow Leopard DVD disk to Macbook Pro. The computer stopped responding and after a restart I got a gray screen with a folder and ?. I have tried 3 different hard drives that have all been used in this MacBook Pro and all installed with Mountain Lion.I have zeroed out one hard drive using Disk Utility and I continue to get failed install. I cannot repair, partition, or erase any drive: Could Not Unmount Disk error on the computer using Disk Utility. I did all repairs using a separate iMac's Disk Utility. The computer is late 2009 Intel MacBook Pro. Please help

pkj0192 wrote:
The computer stopped responding and after a restart I got a gray screen with a folder and ?.
All that says is the firmware can't find the bootable OS it was assigned to. Which you obviously erased.
Hold the option/alt key at boot gives Startup Manager, which you then can select a new/other OS to boot from and set it as the startup disk in System Preferences.
I have tried 3 different hard drives that have all been used in this MacBook Pro and all installed with Mountain Lion. I have zeroed out one hard drive using Disk Utility and I continue to get failed install.
I assume you have used the 10.6 Disk Utiltiy and selected the ENTIRE drive, format Option: MBR and MSDOS, then click Erase and Security Option Zero All Data, and then go back to Partition 1: Option GUID and Format: OS X Extended J?
This rebuilds the GUID and EFI so it's for 10.6 version and removes all partitions on the drive, including the hidden RecoveryHD partition.
I cannot repair, partition, or erase any drive: Could Not Unmount Disk error on the computer using Disk Utility. I did all repairs using a separate iMac's Disk Utility. The computer is late 2009 Intel MacBook Pro.
If you have the drives hooked up to the iMac, Spotlight might be trying to index them thus they can't be unmounted. So have Spotlight ignore everything, turn it off basically.
You can force unmount a drive in Terminal.
..Step by Step to fix your Mac
Are you using the 10.6 white retail disk? Because that's what you need to boot/use on the 2009 MBP, not the iMac's 10.6 disk as those contain machine specific drivers for the iMac only. Don't format the drives on the iMac unless it's also 10.6.
Since your issue appears on three drives, either there is a problem with the machine/cable or perhaps a bad 10.6 disk or wrong methods being used each time.
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Disk Utility: "Repairing disk failed with error Could not unmount disk"

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