Summary: This post introduces 5 solutions you can try when you are unable to mount an external hard drive on your Mac. Also, to avoid further data loss, you can use iBoysoft Data Recovery for Mac to recover lost data from this unmountable external drive first.
- Table of contents
- 1. Why you can't mount your external hard drive on Mac?
- 2. How to fix when external disks won't mount on Mac?
- 3. Conclusion
After you connect an external hard drive to your Mac, if everything is working fine, the operating system will automatically recognize, read, and mount your external drive, as well as show it in the Finder and on the desktop. However, if your disk gives up the ghost just like the users below, the external disk will not be showing up as normal. And if you check it in the Disk Utility, you will find your drive unmounted there.
'I was able to use my 3 TB external hard disk drive to backup my data last week. But now it doesn't mount after I migrate from Mojave to macOS Catalina. I dug around and tried a lot of stuff but still can't mount this external hard drive on my Mac. Can someone explain how to get this drive mounted so I don't lose the data?'
Feb 08, 2020 How to Partition an External Hard Drive on Mac Step 1: Highlight your drive and click “Partition” in Disk Utility. Open the Disk Utility app and highlight your. Step 2: Add partitions and allocate volume for each one. After clicking “Partition”, you’ll see this window. In the Disk Utility app on your Mac, select a volume in the sidebar, click the Partition button, then click Partition. In the pie chart, click the partition you want to delete, then click the Delete button. If the Delete button is dimmed, you can’t delete the selected partition. Click Apply, then click Partition.
Why an external drive is not mounting on Mac?
There are numerous reasons for the external hard drive not mounting issue. The following are a few of the most common ones:
Hardware and connectivity issue
Most of the time, you can't mount your external drive on a Mac just because the connectivity is not in proper condition. This issue may be affected by a loose fitting, a broken USB cable, the wear on USB ports, etc. Sometimes, such connectivity issues could make your external drives keep disconnecting, or much worse, it would make your external hard drive unmountable eventually. After all, it is essential to have a firm and tight connection.
Corrupted disk
Another possible reason for an unmounted disk may come from the problematic hard drive itself. Wonder how could it be? Well, it is possible that you're unable to mount a drive just because it is corrupted and unrecognizable by macOS. You can recall if your external drive has experienced one of these things: an unsafe removal when you are transferring files, an improper ejection, a sudden power outage, or even a virus infection. If so, your disk might be corrupted and it should be the culprit that you are unable to mount your external drive probably.
Incorrect formatting of the disk
In some cases, an unsupported file system will make your external drive unmountable. It is reasonable because if your Mac can't even read your disk's file system, how can you mount and access this hard drive on your Mac? This factor may not be as possible as the other causes, but it does happen.
Unable to mount external hard drives on Mac, how to fix?
Even though the reasons for a not mounting disk are different from case to case, certainly there are some things you can do to fix this issue. The following are five effective solutions to the 'external hard drives won't mount on Mac' issue, and some of them are just basic checks.
Solution 1: Check and fix connectivity issues
The first thing you can do is to make sure that your disk is connected to your Mac properly. Here are some things you can try.
- Reconnect your external hard drive to your Mac and ensure that it fits the USB port snugly.
- Connect the external hard drive to a different USB port or a different Mac. If you are not sure if there is a problem with the USB port/hub, you can plug a working external drive in to a port/on a hub, unmount and eject it. Then plug the unmountable external hard drive into that port/hub.
- Replace the USB cable or adapter in case that it was damaged or broken.
- Connect it to a Windows PC and see if the storage device is powered on and working.
Solution 2: Check the file system of the external hard drive
Well, if you don't know exactly what file system your disk is formatted with while your external hard drive can't be mounted now, you can go to Disk Utility to have a check if it is formatted with an unsupported file system. Remember that macOS is friendly with APFS and HFS+ and is in a neutral attitude with FAT, FAT32, and exFAT. However, it is a different story if you need to access and write to NTFS file system on Mac. By default, macOS only enables NTFS drive read support but disables write support. In this case, you can download a free NTFS driver for macOS to mount this external hard drive in read and write mode.
Still unable to mount the external hard drive on Mac? Then it should be some problems with the drive itself. You can try the following solutions to troubleshoot this problem.
Wait! Have you recovered your important data from this unmountable drive?
Before you go any further to fix this unmountable hard drive, you'd better make sure you have backed up your data on this drive to avoid data loss. The reason is that when your external drive won't mount, you lose the only access to all your files on this drive. In this situation, if you have important files on the external hard drive, any operations on the drive could overwrite the original data and cause irreparable data loss.
Forget to back up before? You can also use Mac data recovery software like iBoysoft Data Recovery for Mac to recover lost data from the unmountable external hard drives.
Mac Not Recognizing External Drive
iBoysoft Data Recovery for Mac is afree external hard drive data recovery tool that enables you to recover lost data from external drives, especially when a hard drive is unmounted, formatted, inaccessible, unreadable, or corrupted. It's fully compatible with macOS Catalina 10.15/Mojave 10.14/High Sierra 10.13/10.12 and Mac OS X 10.11/10.10/10.9/10.8/10.7. In addition to external hard drive data recovery, it also can recover lost data from internal Mac hard drives, USB flash drives, SD cards, memory cards, pen drives, etc.
Tutorial to recover lost data from unmountable external drive on Mac with iBoysoft Data Recovery for Mac
Step 1: Download and install iBoysoft Data Recovery for Mac on Mac.
To use iBoysoft Data Recovery for Mac, you need to install this software on your Mac. You can just download the installation package and install it with no fuss.
Step 2: Launch iBoysoft Data Recovery for Mac.
After successfully downloading this program on your Mac, you can drag it to your Applications folder to install it, or you can double-click its icon to launch it.
Step 3: Select the unmountable external drive and click Scan button to scan all lost data.
When the Mac data recovery software is launched, all connected storage devices will be listed in the interface. You can see the name, file system, and space allocation of your hard drives and partitions. Locate your unmounted external hard drive, select it, and click 'Scan' to scan for lost data. Two scanning modes are allowed: Quick scan and Deep scan. Quick scan mode saves time for users and is applied when data is recently deleted. Deep scan mode finds more files at the cost of more time, and it's used when file system is corrupted or partition table is lost. Anyway, this software will automatically choose the most efficient way to scan for files according to the disk condition.
Step 4: Preview the searching results, choose files you need, and click Recover to get them back.
With the preview feature, you can check whether your files on this unmountable disk are in a good condition or not. It saves time and money for users. The software will show if your file is corrupted so that you would not waste energy to recover it or pay for this data recovery product.
Step 5: Have a check to ensure you have got all lost data back.
Now you either have a copy of a data backup in hand, or have recovered your important files with iBoysoft Data Recovery for Mac. Therefore, you can go ahead to repair this unmounted external drive without worrying about data loss.
Solution 3: Repair the external hard drive with Disk Utility
When an external hard drive is not working properly, you can use the built-in disk repair tool - First Aid to check and repair disk errors.
Step 1: Launch Disk Utility.
Step 2: Choose the unmountable external drive on the left sidebar.
Step 3: Select First Aid in the top center and click Run.
Solution 2: Repair the external hard drive with Terminal
Sometimes, Disk Utility may not function as desired. Fortunately, you can still try to repair the corrupted external hard drive with Terminal.
Step 1: Go to Applications > Terminal
Step 2: Enter: diskutil list (This will list out the available volumes).
Step 3: Check the volume identifier from the table that appears.
Step 4: Enter:diskutil repairVolume [diskvolume identifier]. For example, if the volume identifier of an external hard drive is disk2s, you should enterdiskutil repairVolume disk2s.
Solution 3: Reformat the external hard drive
If yourexternal hard drive can't be repaired with Disk Utility and Terminal, the file system of this drive might be seriously corrupted. The only way to fix this unmountable external drive is to reformat it.
Warning: Reformatting will erase all data on the external hard drive, so please make sure you have backed up important data.
1. Launch Disk Utility from Utilities.
2. Click the icon of the unmountable external drive on the left part of the window.
3. Click the Erase function on the top of the Disk Utility window.
4. Complete the related information (name, format, scheme), then click Erase button.
Conclusion
When you can't mount an external hard drive on your Mac, you can try the 5 methods introduced in this post. But no matter which solution you are going to try, to avoid data loss, you are always advised to back up your files or recover your data from this unmountable drive first with iBoysoft Data Recovery for Mac.
But if unfortunately, none of these solutions can make your hard drive work again, or your disk is not even detected or showing up in Disk Utility, then this drive might be physically damaged. Under this situation, you should send it to a local disk repair service and see if they can help.
Good luck!
Hello,
My wife has an iMac with OS X Lion on it. We partitioned her HD to run bootcamp with Windows 7 to play some games. Bought a Seagate Backup Plus external USB HD for extra space for games on the Windows 7 end and Time Machine for her iMac. Time Machine does not work with the Paragon driver the ext HD came with so I decided to partition it into two parts; one for Mac, the other for Windows.
I looked up about the different HD formats for Mac and Windows. Used Disk Utility to partition the ext HD 50/50. Named the top partition Mac and chose the format Mac OS Extended (Journaled), named the bottom Windows and chose the format NTSF.
After running Time Machine on the Mac partition I restarted the iMac to Windows 7. I did not eject and unplug the ext HD before restarting, not sure if it played into my problem or not but thought I’d mention.
Mac Can't Read External Drive
Once Windows 7 started I opened up My Computer and I did not see the ext HD listed. I ran Disk Management and saw the ext HD listed but it did not show any partitions. Just shows the entire ext HD unallocated.
What do I need to do in order for Windows to see the necessary partition?
Been reading up on the different “options” for the partitions; i.e. GUID and MBR.
Hovsep,
I originally read that link you provided before I was having the issues. I solved the problem yesterday. I changed the Windows partition on the external HD to MS-DOS, ejected the HD, rebooted into Windows 7, plugged in the HD, Windows saw HD right away, went into Disk Management and changed the Windows partition from MS-DOS to NTSF.
Thanks for everyone's help.
Thanks for your feedback:) your valuable solution will help others:)
I am a bit surprised you are having issues because your iMac and OS X version suggests that the drive is most likely formatted using the GUID/GPT partition scheme which Windows 7 should have no issues with reading.
Actually, being curious I just tested it with Lion and Windows 7 (no bootcamp):
I partitioned a drive with one OS X Extended partition, one ExFAT using the GUID partition scheme and Windows detected the ExFAT partition right away.Maybe it's a derp from bootcamp? Anyway, the options you were reading up on are most likely the solution to your problem.
Since you only used Time Machine so far and Windows couldn't even access the drive I assume you have no problem with formatting the drive again losing all data currently stored on it?
Go into Disk Utility, select the external drive and click on the partition tab.
Select 2 partitions etc. as you did before ~ OS X Extended for Time Machine, ExFAT or Free space for Windows. At the bottom click options and select 'Master Boot Record'. Then finally apply the settings and let the drive partition.Maybe bootcamp only likes MBR partitions ~ hope this solves your issue.
have you tried to use windows restore point to revert back just before the problem started?
How to view HFS+ hard drives from Windows
http://www.macbreaker.com/2012/02/access-mac-os-x-partition-from-windows.htmlNot quite what I am asking.
Bought the external HD because it is compatible with Mac and Windows because of the pre-installed Paragon driver (allowing Mac to read and write on NTSF). However, there was a note saying Time Machine wouldn't be able to be used. So I reformatted the external HD.
I'm wanting to know why the partitioned disk is not showing up in My Computer. In Disk Management the entire external HD is unallocated. Only option when right clicking not grayed out is to format it.
how you reformatted the external hard drive? which file systel
The best ways to format an external drive for Windows and Mac
http://howto.cnet.com/8301-11310_39-57401784-285/the-best-ways-to-format-an-external-drive-for-windows-and-mac/