Q: Anyone else having problems with external disks unmounting randomly/suddenly on Mavericks?

I'm also having the same problem, I have a WD 2TB my book essentials connecting via USB 3 that keeps unmounting it's self. I just connected it to a windows machine and it works without a problem. However I also have another WD 1TB drive that's connected via FireWire 800 with no problems. Has anyone figured out what's going on here?  I am not even able to gain access long enough on my Mac to reformat it.

Yes, I am having the same issue on a mid 2012 macbook pro after upgrading to Mavericks.  I am using a Kingston USB3 card reader, and had no issues copying large amounts of data before upgrading to 10.9

Now, It will randomnly eject the disk.

Resolved for me at least

I went back to Mt Lion and got the OS nice and clean.  Updated Mt Lion with everything apple wanted to send and then did a Maverick 10.9 upgrade. 

I did a Time Machine backup is 2 hours.  The external (unpowered) that was disconnecting randomly took the backup and stayed connected for a full 24 hours.

so

Fingers crossed we are fixed at the present time.

Next....

I am trying to repeat the same steps looking for the same results

Then I will try the Mt Lion iMac......

I have the same issue with my two WD drives. It drives me mad, anyone in touch with Apple on this?

I just installed the gmail-related update (http://support.apple.com/kb/HT6030), not sure it has anything to do with it though. I disabled dropbox syncing now too, let's see if it helps.

I will consider this solved

I have now repeated the fix 3 times (2 HDDs on a MacBook and 1 iMac)

Is you have a good Mt Lion load and do the upgrade (suggest downloading and keeping a copy) Maverick seems to lose this problem.  I even di a full fresh load of mt lion and then did all the upgrades.  Then loaded 10.9.  All my loads are now working flawlessly.

I have what appears to be the same problem, but with a brand new MacBook Pro (15" late 2013) that came from Apple with 10.9 installed - no upgrade involved.

The external drive that keeps ejecting is Thunderbolt (LaCie 5Big), also brand new. I had the drive plugged into a powered hub (CalDigit) but changed it to plug it directly into the MacBook pro hoping that would make the problem go away.

It didn't.

This is a massive pain. I'll go and report this to apple, but I think this is a buggy OS, not faulty hardware.

Yes my Drobo is directly connected to my Mac Mini via Thunderbolt. The problem for me only happens when waking from sleep. When I wake from sleep I get the " Disk Not Ejected Properly" message.The drive does wake and is mounted on the desktop after sleep. It actually seem to to be ejected although I keep getting that message.

My iMac is also brand new. I've only installed 10.9 Mavericks, almost the same day on a fresh OS.

This must me a OS related

Today I got a warning that time machine failed, and that the disk is "read only". I can't access the data on the disk anymore and it only shows up in disk utility. I've tried to repair the disk, but it failed.

So, i've just lost 1,5 tb of data.

I think the problem is related to this discussion https://discussions.apple.com/thread/5475136?start=0&tstart=0

I suggest people unplug their external hard drive immediately, and wait for a fix.

I'm still having this problem. Still no fix from Apple!

anpie 

I have the same issue with my two WD drives. It drives me mad, anyone in touch with Apple on this?

eM_NL 

So, i've just lost 1,5 tb of data.

http://community.wd.com/t5/News-Announcements/New-Release-WD-Drive-Manager-for-M ac-Version-3-1-0-11-25-13/td-p/628437

Dear WD Registered Customer,

As we previously announced, Western Digital received reports of Western Digital and other external HDD products experiencing data loss when updating to OS X Mavericks (10.9). Our investigation to date has found that for a small percentage of customers that have the WD Drive Manager, WD Raid Manager and/or WD SmartWare software applications installed on their Mac, there can be cases of a repartition and reformat of their Direct Attached Storage (DAS) devices without customer acknowledgement which can result in data loss. We have an updated version of the software that fixes this issue. We strongly recommend that you install this updated software. Please contact our service and support team with any questions.

Below are links to download the software:

• WD Drive Manager for Mac Version 3.1.0.
• WD SmartWare Version 1.3.6 for Mac 10.5-10.9.

Sincerely,
Western Digital

What about our issue with the ejecting HDs. When is apple going to fix this?

others are trying to diagnose same on another thread, however no information yet from Apple on same.

Awesome, thanks! Do you know which thread is primarily focusing on this?

Problem here as well with 2010 Mac Pro. It actually started when I updated to Lion where I got disnonnection several times a day (only for FireWire drives, moving drives to different firewire port makes it more or less frequent). Montain Lion greatly improved it (disconnect 1-2 times a month). Maverick is back to several times a day......Moving the drive to USB or eSATA makes the problem go away. I have this problem with OWC Qx2,Elite and Rack, LaCIE, WD, Seagate and MacAlly drive enclosures, brand does not matter, only the use of FIreWire causes the problem. The problem shows more frequently when computer sleeps/wakes but can happen indenpendently of sleep/wake.