External hard drive won't mount in high sierra

tried doing the same by turning off all results for searchlight...that did not help. I am having trouble mounting 2 Seagate USB drives that are formatted NTFS. They show up in the disk utility app but can't be mounted. Downloaded paragon NTFS software and it can't mount the drives either!!

All of my external drives worked fine until I upgraded to High Sierra. After the upgrade, the only drive that would show up was my older WD external (USB 2.0). I have a 3.0 USB caddy with a Hitachi and Seagate drive that appeared to be invisible to my iMac. Nothing I tried would make them show up and mount. After a few weeks of reading these forums with people having the same issue and desperately looking for a solution, I decided to plug my 3.0 drive caddy in to my powered USB hub (also older and not 3.0) and the drives mounted with no problem. It would appear to me that High Sierra has a problem with the USB 3.0 protocol.

I am having the same issues with all my external drives. Either on MacBook Air or MacBook Pro. It's such a **** joke. But, hey, Apple: we have things like touchbars with smileys now. Who needs a machine that actually works?

Maybe this will help some users seeing these strange High Sierra external drive mounting issues. I have an external Seagate that I plug in for Time Machine back ups (named Seagate). If I plug in a flash drive that I use to move files to another Mac occasionally, it does not mount correctly. The icon comes up on the desktop, but the name is incorrectly shown as Seagate - when the Seagate is not even connected anymore. If I try to open with Finder or by double-clicking the icon, it will not open. My solution - I reformatted the flash drive (using disk utility) to use FAT32 formatting. Now the flash drive is properly recognized and mounted when it is inserted. Mac OS engineers need to sort these external drive mounting issues out, as this thread shows a bunch of people having problems.

I have had this problem everyday, and I have found a few temporary "fixes".

1. Reseting your USB - Do this by restarting your computer and immediately holding down 'Command, alt/option, p, r' once the scene goes black. Your computer will doing its usual ding, light up, then power down and ding again. Then release the input. I have found this works 2/3 of the time. Sometimes I have to do this twice, or it doesn't work at all

2. Plug in a USB 2.0 Hub and then plug in your drive. For some reason this has worked for me. My issue with this is I am editing 4K files and USB 2.0 is slower, but it is better than nothing. I have found this also does not work when your plug your drive into your extra keyboard USBs. Mine could just be USB 3.0 though.

3. Power down your Mac and unplug the power (if it is not a MacBook). I have heard this works for some people, though the 2 times I tried it, it did not.

It is unfortunate that this is an issue, and it has cost me time to fix when I could have been working. Once I am able to get my hard drive to connect, I am not able to reconnect it again once my computer goes to sleep. I hope Apple comes out with a patch for this soon. I have ordered a new hard drive and will try to configure it to High Sierra, and hope I no longer have this issue.

As of today this problem still persists. Having done a clean install on a new 2017 MBP, I attached a number of drives to make backups. None of the drives would function normally, except a Drobo which I have used for both Time Machine (TM) Backups and media storage. It has worked almost flawlessly with my 2009 MBP for several years. Having completed my first TM backup yesterday evening, I switched everything on today only for the TM volume not to mount. Disk utility didn't work (first aid, erase or anything else) and I couldn't eject the drive either. When I reattached it to my old MBP I found that the Drobo had been corrupted and have spent several hours trying to get it to work. I found at one point that the TM volume had been reformatted to APFS - apparently as a consequence of setting up a new Time Machine folder (Apple Tech advised me that this journaling is automated - I certainly wasn't given a choice... or a warning). This may be what has caused the issues with the Drobo and is surprising given that TM will not work with APFS!

2 calls to Apple Tech Support failed to resolve the problem and it was clear that they consider problems with 'third party' hardware to be outside their responsibility (so hard luck, apparently). In other words, the MacBook Pro itself is working with High Sierra and problems with hardware outside the Apple eco-system, especially with 'legacy devices', are someone else's problem. I'd pretty much accepted that I needed a new MBP and monitor (+ hub, adapters etc), but certainly didn't expect to have to replace all of my backup drives as well because of an issue with OS compatibility. This seems ridiculous and whilst I like the 2017 MBP in itself, it (and its collection of hangers on) may be going back.

I'm posting this to alert anyone looking to switch across to be mindful that until a fix is confirmed that High Sierra may pose a risk to your data should you attach one or more of your existing drives. It's certainly cost me a lot of time and grief.

Apple... it just works!

Just a brief update. Once my Drobo had finished its own personal meltdown after the Time Machine folder debacle, I was able to reset it to the factory default and reformat it using Drobo Dashboard (losing all of my stored data in the process of course). Other than a single incidence of strange behaviour where it lost, re-found and then rebuilt a drive, it now seems to be behaving normally.

A new (late 2017) WD My Passport Wireless Pro also works fine, but all legacy drives (those a couple of years older or more) continue to present problems and will need to be cleaned and disposed of.

This is exactly the problem I'm seeing as well with my Seagate external drive.

Am waiting to hear back from 3rd-tier Apple Support. Spent 3 hours on Friday with them documenting the issue, but nothing worked.

Hi Tim

I've got the exact same issue.I can see the hard drive in DU and run a check/repair but it doesn't show in finder and I can't access any files. have you found a fix .

I also try unticking everything in spotlight it didn't help at all

same as you it worked fine before I installed High Sierra, it's really terrible that mac can be so difficult to connect with other systems sometimes, such a waste of time for something that should take 5 mins...

Thanks!

Cyndie

I tried your solution and it worked! As you said, turned everything off in spotlight search results, then unplugged my external drive and plugged it back in and the disk mounted and was fully accessible. Very strange. Am about to restart the computer to see if it stays that way.

I have the same problem. External 4T Seagate disk drive. Running High Sierra on a 2015 MacBook Pro. Disk Utility can't mount it or repair it. TechTool Pro 9 can't repair it. My computer keeps warning me that it has been removed without ejecting it when it's still plugged in! Now it won't come up on the desktop at all. This is my Time Machine backup external disk and I need everything that it holds in addition to the backups. Please, Apple, help us with this!!!

It seems a lot of people having the problem have their time machine backup on the drive, as me. I tried to remove "dataless" snapshots as explained in this article and i could mount my drive again afterwards : https://frenchw.net/en/tags/timemachine-en/

I have a LaCie Porsche external hard drive that experienced this same issue. It is partitioned, and the HFS+ partition (with my Time Machine backups and other important content) showed up in Disk Utility as greyed out, refusing to mount on a MBP running High Sierra. I could hear the device spinning, but it seemed stuck.

I typed "sudo lsof|grep disk2" into Terminal, which allowed me to see that the drive was in the middle of a self-initiated "fsck" (file system check) process. I allowed that to run for several hours overnight. By morning, the "fsck"-ing had stopped, and both partitions were available to use.

I had this error and as mentioned @abuohp this solves my problem. Go have a look :

English : https://frenchw.net/en/2018/04/13/correct-the-macos-error-snap_metadata_val-obje ct-invalid-extentref_tree_oid-0x0/

French: https://frenchw.net/2018/04/13/corrigez-lerreur-macos-snap_metadata_val-object-i nvalid-extentref_tree_oid-0x0/

Hope this helps

FrenchW

Hello. I'm not sure if I can help, but here was my situation. For some unknown reason my WD 1TB suddenly stopped "mounting." I'm using MacOS version 10.13.4 (High Sierra). I found one of my older forensic applications called Disk Arbitrator. The application recognized my WD 1TB external hard drive as "unmounted" and I was able to "mount" the drive using this application and I was able to subsequently make a copy of the drive (data) using a software copy program and then "restore" my original drive from the backed-up drive using the "restore" function in Apple's Disk Utility application. The Disk Arbitrator program was an older version (v0.2); I could not figure out this process using "newer" version of this program. BTW, because my drive would not mount on my iMac or MacBook Pro, Apple Tech reached the conclusion that the drive had to be bad and unfortunately I was going to loose all my data. Anyway, this worked for me and I hope it may help someone else. Forgot to mention, Apple Disk Utility was able to see the "unmounted" drive and I was able to perform a "disk repair" check on the drive, but Disk Utility was not able to "mount" the drive - came back with an error message regarding "unable to mount" the drive. Hope this information is helpful.