Q: External USB Hard Drive not showing up, after Yosemite update

I ran to try this. It does show my external hard drives but I cannot access them. It makes my OS EXTREMELY unstable. Slow from sleep. Still not fixed. :-(

Adding more information to help fault isolation:

- Just purchased new iMAC 27 5K

- Pre-installed with Yosemite

- Firewire -> Thunderbolt connection to back of unit (5K does not support direct Firewire as my previous iMAC did)

- All drives are Password Protected and the WD Unlocker shows up consistently per drive

- Even drives that are Firewire daisy chained successfully display WD Unlocker

- However, after unlocking the drives, the Drives themselves do not show up.

I have:

Power cycle the iMAC

Unplugged the power

Swapped the external HDD across several ports.

The Yosemite HDD support is absolutely broken.

How in the world did this get past Beta Testing!!!

Thanks for this. According to other posts here, this wasn't a problem in beta. Were I a conspiracy theorist, I would be tempted to think this is an antitrust law issue. But I still have faith.

Just found this in WD thread:

http://community.wd.com/t5/External-Drives-for-Mac/WD-my-passport-not-mounting-o n-macbook/td-p/812515/page/2

I'll continue to monitor both support sites, but for now, 5 External HDD are dead in the water, and I have no Time Machine support.

I'm unable to provide assistance to anyone, but on the *tiny* chance that someone at Apple is reading this, I wanted to report that I am also experiencing the same issue as many others are here. 2013 Macbook with retina, came pre-loaded with Mavericks, I updated to Yosemite a few weeks ago and had no problems recognizing external drives (thumb or otherwise) in Finder; however, I just now, today, downloaded and installed updates from Apple, and it is no longer recognizing my external hard drives, despite having tried every possible fix detailed on these pages. My external drives have a lot of important information on them and I need access to them - ***?

i had the same problem on my late 2013 13" MacBook Pro after installing OS X Yosemite. Now i´ve installed Kext Utility and it worked for all my Western Digital hard drives (MyBook, MyPassport) after reboot all hard drives were in the the finder, hope this helped you

I am having the same issue on my mid 2014 retina MBP. Somewhat differently than other reports, this came with Yosemite already installed and, as such, was not upgraded from Mavericks (perhaps indicating that this isn't some sort of failed upgrade issue and is purely a Yosemite issue).

This is my first mac and I'm trying to copy over a decent bit of data for work and thus far have been unable to. I'm also using an external WD Passport 2.0 TB drive on USB3. Drive shows up fine in disk utility, I just can't mount it. I have tried running KextUtility and restarting to no effect. Based on the lack of confidence in the Onxy suggestion I haven't tried that yet as I don't like mucking about in the OS without knowing what I'm doing. I have remounted the drive in linux on my other PC and everything looks just fine with it there.

Apple your lack of attention to what should be a serious software issue is noted, I genuinely hope that this is an isolated issue and not the start of a pattern which will quickly lead to me spending my money elsewhere in the future.

Same problem!  Mid 2014 MacBook Pro 15 inch Retina 2.8 GHz with Yosemite.  External hard drive mounts and works fine on my old MacBook, will not mount on the new one.

If I plug and unplug the external hard drive several times (3-5) sometimes it will mount.  I then run Disk Utility and repair the disk, though it always says there are no errors.  Sometimes if I leave the hard drive plugged in, it will mount 20-30 minutes later.

Once I get the hard drive to mount the first time and am able to use it, I can freely unmount and mount without problems.  However, if I restart the computer, it will no longer read the external hard drive and I have to start all over with the steps above.

This seems to be a pretty big issue and I know I personally have tons of data on several different externals.  Not being able to access that data is not only scary, but unacceptable.  We need a fix, Apple!  I don't upgrade and buy a new computer often, making the jump to this new MBP was exciting and a big deal for me- this issue has really tarnished that.  While this new computer and Yosemite sure looks pretty, I'm a lot more functional on my old one where I can get to my stuff...

To add another twist in the plot:

One of my external drives won't show up when plugged in directly, but WILL show up when it goes through a USB splitter.

Brand new Macbook Air

Installed Yosemite as soon as Air was purchased

One drive has usb 3 blue plug and will show up

One drive has usb 3 blue plug and won't show up

The splitter as USB 2 white plug

So, it doesn't seem to be due to USB 2 vs 3 for me.

I don't know if anyone has mentioned this yet, but after hours of searching for an answer as to why my external hard drive did not show up on my desktop after upgrading to Yosemite, I clicked on the Finder, clicked on Preferences and under the General tab there's a section that says, "Show these items on the desktop," where I simply checked "External Drives." All is well now!

I don't know if anyone has mentioned this yet, but after hours of searching for an answer as to why my external hard drive did not show up on my desktop after upgrading to Yosemite, I clicked on the Finder, clicked on Preferences and under the General tab there's a section that says, "Show these items on the desktop," where I simply checked "External Drives." All is well now!

Good thinking, but unfortunately my box was checked to display externals.  Different issue.

This thread:  External Hard Drives not Mounting after Yosemite Upgrade reports that running a third party utility "Kext Utility 2.6.1" fixes the problem.

I have a Macbook Pro & a Macbook Air, and neither would recognize thumb drives that previously worked, nor external hard drives after upgrading to Yosemite.  The drives would not appear in Finder or in Disk Utility.  The Air has a stock SSD, and the Pro has a 3rd party hybrid drive.  I am wondering if a common theme of this issue is having a SSD. 

I was able to get my Air to recognize and format a new hard drive that was pre-formated for Windows.  I have not yet tried out a thumb drive on the Air, and I haven't tried this fix on my Pro.  I threw everything at it at once, so I'm not sure which piece of this did the trick, but something in here seems to have done it for me.  Here's the path I took:

1:  Verify Disk (in Command-R recovery mode).

2:  Repair Disk

3:  Verify Permissions. 

4:  Repair Permissions

5:  Let it startup normally, letting everything load, then shutting down.

6:  Zap PRAM three times in a row.  Let it startup after the third time, letting everything load, then shutting down.

7:  Reset SMC

I will try this out on my Pro later today and report back if I was able to duplicate success.

John Strung: Thank you for the helpful suggestion. Unfortunately this hasn't helped everyone, myself included. This was previously suggested in this thread and I was hopeful it would solve my problem, sadly it did not. I still encourage everyone to give Kext Utility a go, however many of us are still hoping that Apple looks deeper than that as clearly there still is an underlying problem.

tackle78: This sounds like a new issue as far as I can tell; though it definitely appears to be similar to the issues that several of us here are facing. In my case, and I think others, the drive itself is being seen in Disk Utility, however we cannot mount it even though the partitions are known to be in good shape. My best guess is that our issue lies in the partition table and I've been experimenting trying to figure out what can be done a bit on my own. Your issue sounds like it lies a step or two deeper as the OS itself isn't even acknowledging the drive's presence. Just for the **** of it, its probably still worth running Kext Utility to see if that changes anything for you. If it doesn't I would think you should see if you can find any other reports of the OS failing to see the drive at all. It is odd that they show up just fine in recovery mode as that should have the same kernel drivers (or perhaps fewer) loaded. I'm a linux guy myself so I'm sort of getting used to the OS X way of handling things. If you are unable to find similar behavior reported you might consider starting a new thread as I don't think your issue is the same that many are experiencing here beyond the end result, i.e. you plug in a drive and can't access it.

Cheers