I've been using my Seagate Portable Media 500GB external hard drive for Time Machine on Mountain Lion.
Last week, Time Machine's backup failed, with the message "Unable to complete backup. An error occurred while creating the backup folder."
Using Disk Utility, I verified the disk which asked me to repair it. On trying to repair it, I received the message "Couldn't unmount disk". I received this message also when trying to Erase or Partition the drive and I don't know how to take it further.
The drive is still visible in Finder and I can still access its contents.
I've also tried using a new power cable for the drive and I'm having the same results.
Any advice would be great!
Just an update:
If you run into trouble after repairing the Disk with TM trying to do a full new backup, try James Pond's method of doing a Total Reset. This has got TM back doing incremental back ups vs a new backup.
Hi Joe, I've tried both of these and I seem to still be having the same problem. After the Time Machine has done a few backups and seems fine, it "corrupts" and has to be completely wiped and start all over! I've tried the total reset and fully repairing/erasing the drive, to no avail.
This is becoming annoying as I have to do a full erase and full Time Machine backup of the drive every time it does this.
Any more suggestions?
Do you have any other external drives plugged into (daisy chained) your Time Machine disk. The reason I ask is I've found out what my problem is when TM says it's not able to do a backup. I have another external drive plugged into my TM disk. Whenever I unmount the second drive, my next TM backup will not complete. I boot into the Recovery HD/Repair Disk and then TM will work perfectly until I unmount the second drive the next time.
I assume you have the drive formatted to HFS+. Below from Seagate:
* The drive must be reformatted to HFS+ in order to use backup software for Mac or Time Machine software
Please follow this step before atempting Joe Gramm's "boot into recovery" method.
1) Keep your external hard drive plugged in.
2) Restart your computer.
3) Go to Disk Utility and eject the drive.
You should have no problems carrying out Step 3. If this fails, you'll have to rely on Joe Gramm's advanced method.
Hope you (and anybody else) have benefited from this simpler method! Don't forget to like or put "This solved my question" or "This helped me"!
from Galaxy User