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

I also have the same issue, with two different hard drives. Both are new and run with USB 2.0. They were working perfectly fine minutes before I started the upgrade to Yosemite.

I have a MacBook Pro (15-inch, Mid 2012). The two drives are Western digital and Seagate. The link in the above answer did not solve anything for me.

Same here. No USB device -- or optical disc, for that matter -- automounts any longer. (Haven't tried a FW drive yet.) I have to manually mount anything I'm using in Disk Utility.

I got one drive to work by plugging it in immediately after a restart. However I have gone to put it in again after the computer has been asleep, and it is not recognised.

Since Macs can't write to an NTFS volume without 3rd party software you may have to reinstall that software before you'll be able to mount and see the drive.  You did have such software installed before the upgrade, right?

I have an external Blu-Ray drive.  It doesn't even show up in Disk Utility anymore

I could have sworn that I did this when I first saw the problem, but I guess I didn't.  I plugged my drive directly into my computer (bypassing my USB hub) and now it works fine.

Sterling, the link you provide is to a legacy article, and this is a little more serious than "check the connections and check the power." Any other suggestions?

Same problem. Thinking of using Time Machine to return my computer to yesterday, when my two external hard drives were working fine on Mavericks. I hate to do that, though. I like what I'm seeing of Yosemite.

Yeah, I've now found it's affecting my ipod, because I had it set up to have external drive mode. This is a pretty shocking issue with Yosemite.

NormHouser - I considered using time machine to go back too, but It's not even recognising my timemachine drive!

yosemite won't work with ntfs drives for some reason, i've had the same issue with my toshiba. i thought ok lemme buy another one, and transfer it over maybe it's a driver issue which i've tried over and over, apple support can't figure it out.

here's a simple fix, but the problem is i have an external where all my photography and video files are stored, so i can't access them right now and it's making my life ****.

http://guides.macrumors.com/Formatting_an_External_Device

that does work and make the drive mountable now, but problem being i can't obviously reformat the old drive and lose everything. once the new drive is formatted for mac i can't plug it into a pc to transfer the files from. which is the only problem now. but formatting the drive for mac only DOES work. but you're just screwed and not able to use it ntfs. hope the link helps SOME people.

Also, just as a side note. This morning my external drive stopped working. I tried a few things, some utilities and such and figured that my enclosure had failed. After purchasing a new one, I found that it still didn't work. I had tried the usb port directly adjacent to the original port on my mac mini, and you guess it, it worked. It seems that half of my usb ports now no longer work. I have reset the pram and other things but still no luck. Tested with a low power device (thumb drive) and it lights up but still no joy. When I searched the other forums I noticed that others are having the same odd issues.

Thanks All.

TH

yosemite won't work with ntfs drives for some reason,

Macs were never able so write to NTFS drives without 3rd party software.  Possibly the install of Yosemite removed the software you had been using previously which killed the ability to even view the drive.

AHHH HAA! I did get notifications some things were incompatible after the install but didn't recognize any of them. I was also told the app paragon? Will work to fix the drive read issues?