Mac – Failed to mount partition of Mac OS Extended (HFS+)

external-diskfilesystemhfs+macpartition

As a matter of fact, my 1 TB External hard disk has three partition: "MAC OS", "NTFS" and "FAT32". All of the partitions worked very well in the past.

However, I just discovered that my Mac OS Extended (HFS+) formatted "MAC OS" partition could not be mounted, although the other two partitions were seemingly fine. I tried to repair the partition with Disk Utility but it failed. I have no idea why this had happened to my hard disk, since I have not done anything disruptive to my hard disk and my MAC OS partition.

I have only done two things before I discovered that my MAC OS partition was no longer working:

I installed the Apple Security Update 2015-002 when my hard disk was plugged into my Macbook air.
I tried to move some files from my "NTFS" partition to another external hard disk. But it failed because of unknown reason.

This is what I got when I did the "diskutill info" on Terminal:

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This is what I got when I tried to repair my partition:

enter image description here

How do I solve the problem and recover my "MAC OS" partition and get my data back?

Best Answer

Got it back when giving even the hfs+ partition a drive letter in Windows drive-management, did a chkdsk there. (It was an external usb-drive 3Tb)

Related Solutions

Mac – Reformat a Partitioned Mac OS Extended External Disk

This is an example of a procedure to erase an external disk containing a single encrypted partition.

Open the Disk Utility application and highlight the "Logical Volume Group" representing your external disk. An example is shown below. (Hint: click on image for a better view.)
Next, click the Info icon to get the pop up window. Note, in the example shown below, the "Physical Backing" is disk1s2. This means the physical disk number is 1. The "s2" suffix can be ignored. Your numbers may be different.
Next, highlight the "Encrypted Logical Partition" as shown in the example below.
Again, click the Info icon to get a pop up window. Note the "Disk Identifier". In the example shown below, the value is disk2. Your value may be different.
Close the Disk Utility and open the Terminal application. Enter the following commands. If your numbers differed from mine, make the appropriate substitutions. If prompted, enter your login password.
```
diskutil  unmountDisk  /dev/disk2
sudo  gpt  destroy  /dev/disk1
sudo  gpt  create  -f  /dev/disk1
```
When I entered these commands, I saw the following in the Terminal window.
```
Steelhead:~ davidanderson$ diskutil  unmountDisk  /dev/disk2
Unmount of all volumes on disk2 was successful
Steelhead:~ davidanderson$ sudo  gpt  destroy  /dev/disk1
Password:
Steelhead:~ davidanderson$ sudo  gpt  create  -f  /dev/disk1
Steelhead:~ davidanderson$ 
```
The distutil command must successfully unmount the disk in order for the gpt commands to work. If the disk will not unmount, then some window needs to be closed. Do not proceed with the gpt commands, if you can not unmount the disk.
If successful, you should see a result similar to what is shown below. The result shown is a 4GB flash drive with no partitions. You can either add a partition or repartition the entire drive.

Can files be exchanged between FAT32 and HFS+ partitioned drive

It might make sense to make the entire drive FAT32 to ensure readability between systems, unless there is a need for having multiple partitions not described in your question. As for the specific answers,

Yes, dependent on #2
The files MUST be moved on a Mac because a PC cannot read an HFS+ partition by default and even then, cannot read without special software. Your friends would only be able to read the FAT32 portion of the drive.
Yes, your older Macbooks should be able to read the partition, and compatibility exists all the way back to OS 8.1 (source)

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