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reformatting an external hard disk

I recently bought a second external hard disk. The box said it would need to be reformatted for Mac. I tried using disk utility. It wouldn't backup from time machine. I searched previous questions and found this:


Drive Partition and Format


1. Open Disk Utility in your Utilities folder.


2. After DU loads select your external hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.


3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Apply button and wait until the process has completed.


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 Security 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.


But that still didn't work. I keep getting this error message:


"The backup was not performed because an error occurred while copying files to the backup disk. The problem may be temporary. Try again later to back up. If the problem persists, use Disk Utility to repair your backup disk."


I've gotten this message 4 times. It's a 2007 macbook pro, running 10.7.5. USB 2 (hard disk says usb 3.0 + usb 2.0).


thanks for any help you can provide

Posted on Jul 7, 2014 10:57 PM

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17 replies

Jul 7, 2014 11:03 PM in response to grawingirl

The new drive may be formatted NTFS in which case the steps you followed (they came from me 🙂) will not work. If the drive is formatted NTFS, then you must first reformat the drive to FAT (MSDOS.) Only then can you alter the partition map from MBR to GUID then format the drive to Mac OS Extended, Journaled.


You must do this because OS X cannot write to an NTFS formatted drive.

Jul 8, 2014 11:26 PM in response to Kappy

To be clearer about what's happening, Time Machine looks like it's backing up, then after hours, I get the error message.


<<Is it partitioned GUID and formatted Mac OS Extended, >>


The partition, untitled 1 shows formatted Mac OS Extended, but I have to go to the disk listing to see GUID. I tried copied a couple of files to the Untitled 1. It copied okay, I was able to open both a pdf file and a photo, but the little wheel is still spinning on the disk icon in the list of apps.


Is there any way to test to see if the drive is defective? It was a cheap drive $99 for 2 T.


I just noticed another file on the partition, when I opened it it gave the name of my computer and then, 2014-07-08-161522.inProgress. To me it looks like the hard drive is still trying to back up. Looking at time machine, it's spinning as well. I'll let it continue unless I hear differently.


Appreciating your help.

Jul 8, 2014 11:39 PM in response to Kappy

Perhaps I did interrupt it. I just saw the error message and assumed the disk was not working. Perhaps the error message was an error?


It's backing up 126 gb. The progress window says it's backed up 24 gb and has 2 hours to go. Before it was saying things like a day, or 23 hours.


I'll wait to see what happens, with fingers crossed.


Good to know the disk sounds ok. The shop is more than an hour away over country roads.


Since I've been typing this it shows a total of 29.5 gb backed up, so it seems to be doing something.


Thanks for your help. I'll check it later tonight.

Jul 9, 2014 12:12 AM in response to Kappy

Okay, time machine just quit on me with the same error message. The little ball is no longer spinning on the ext hd icon in the list, although the folder is still there that shows back up in progress. I took a screen shot of the file listing:

User uploaded file


Sorry if this is too much info. I just don't know what would be helpful.


Thanks some more.

Jul 9, 2014 8:13 AM in response to grawingirl

Make certain that your laptop is plugged in to power, and then in System Preferences > Energy Saver, set Computer and Display sleep to never under the Power (not battery) category. Uncheck put hard disks to sleep when possible. Unless you do this, your machine will doze off during the Time Machine backup.


Also, in your System Preferences > Time Machine panel under Options…, click the plus button and add your external Time Machine drive in here, to exclude itself from backups.


When I recently acquired a new MacBook Air, I needed a new Time Machine backup drive. I purchased a 2TB Seagate USB2/USB3 drive that was preformatted for Microsoft’s NTFS. Here is how I reformatted it for Time Machine use.

  1. Disk Utility

    Selected the drive name

    1. Partition
      1. Layout as 1 Partition
      2. Name as TimeMachine
      3. Format as Mac OS Extended (Journaled)
      4. Size as default (full drive)
      5. Options as GUID
      6. Apply
    2. First Aid
      1. Verify Disk
  2. System Preferences > Time Machine
    1. Select Disk...
    2. Use Disk
  3. Slide Time Machine from OFF to ON.

Jul 9, 2014 6:29 PM in response to VikingOSX

yes, it's been plugged into power with the little plug icon showing.


Okay, the display was set to sleep. changed that to never just now. Unchecked put hd to sleep when possible. I think I did all the rest of what you listed. Will try to back up now. If still showing an error message will redo your reformatting list.


Thanks. It was good to find something to change before trying it again.

reformatting an external hard disk

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