Q: Mountain Lion improperly ejects external disks

i think you missed that connected through a hub, or directly via USB- it still ejected, and yes after a reset of both the SMC/PMU.

The powered dock, through the hub worked- none of the others.

Could this issue be caused by a USB 2.0 vs. 3.0 clash of some kind. I know 3.0 is supposed to be backwards compatible, but... if a hard drive is USB 3.0 and the hub is USB 2.0, could that be the cause?

Consider yourself lucky - I've tried two powered docks, one cheap Chinese made one, then a Staples brand one (still connected this way), but both are USB 2.0. Perhaps the trick is that it's a USB 3.0? I don't know. I have not tried restting SMC/PMU, I'll give that a go and see what happens.

dude- USB 3 is the key.

Nextstar is a pretty inexpensive brand- $19 CDN for a dual bay powered dock.

Cured everything.

let's take a step back for a sec

3 questions

• Hardware used?
• OS running? 10.8 I know
• ability to reproduce problem?

1) Mid-2012 Macbook Pro, OS 10.8.3;

2) 2008 MacBook, OS 10.8.3

3) I cannot manually reproduce the issue; it shows uprandomly. Lately, it is occurring on my MacBook about every other day, but not at all on my MacBook Pro.

My situation has gotten better. Two days and no ejecting yet. I reformatted my WD USB3 passport. Reintalled the WD firmware. Then I went into the Spotlight settings under preferences and disable spotlight searching for my external WD passport. So far so good. I will report back if it doesn't work.

Nevermind. Still ejects. Strange how my left port does not do it but my right port does. Its fine on the right port with a powered hub though.

I had the same problem for the past two weeks on my late 2012 iMac.  It was fine for the past 3.5 months then started to eject external hard drives whether they were connected to the back of the iMac or through the powered Belkin hub.  This is what I tried all to no avail:

Repaired disk, reset PRAM/SMC, performed a safe boot, unchecked the "put the disk to sleep when possible".....though that made the least sense since that is only useful for the main hard drive, ejected all disks manually and then shut off the power to each hard drive for a couple of minutes then reconnected them to the computer and the Belkin hub........

What worked for me was a permission reset: first I used CMD+R after a restart went into Terminal typed................resetpassword (no space)  then a dialogue box comes up select the main hard drive at the top and select reset permissions/ACL at the bottom of the dialogue box.  After that was complete I restarted the computer opened disk utility and reset the permissions for the main hard drive.....note the reset of permissions/ACL with CMD+R resets the user permission folder.  It has been a couple of days now and I have slept it multiple times through the day and over night without a problem.  Hope this helps......it was truly frustrating

I have activated a program I acquired from Lighthead called "Caffeine". Caffeine is a tiny program that puts an icon in the right side of your menu bar. Click it to prevent your Mac from automatically going to sleep, dimming the screen or starting screen savers.  So far this has prevented my external backup drive from disconnecting becfause of the4 sleep related problem noted in this thread.  I am using a Thunderbolt to Firewire dongle to connect to my backup drive and a 2nd harddrive I use for video.

Hope Apple or some 3rd party vendor can get this problem corrected.

Did you try to repair the permissions as stated in my prior post?  That has worked for me............. It seems unreasonable that you would need to use Caffeine, which is a great little program, for this particular problem.

I agree. Using Caffeine to deal with this issue makes no sense, when you can simply use  your Energy Saver pref to control sleep, dimming, etc.  But, this approach had been tried and it was NOT successful for dealing with this intermittant issue.

I still think the issue may be related to power flucuations over the USB cable to my backup drive. When I have my external drive connected directly to the computer, I don't seem to get the "improper ejection" error message. Only when it is connected via a USB hub do I see this occasional error message. And every time I see the message, the drive has already re-mounted itself. Very strange behavior.

I have not tried the "try to repair the permissions" process you mentioned.  I have an Apache web server, PHP, and MySQL database running on my late model 2012 iMac that I migrated from my Snow Leopard McBook pro.  I am  concerned that I may corrupt permissions set on any of these products files or folders.  Using "Caffeine" is a simple solution that ensures I do not inadvertently corrupt something by changing permissions that may render my web or database server to fail.  My problem only occurs as a result of the computer going to sleep.  After which I literally have to power off the external hard drive and power it back up to get it recognized, even thought it's icon still appears on the  desktop.

One other idea, I am curious about is whether you using a program like XtraFinder for tab style browsing in Finder.  If so, I would recommend at least for the time being not using it and see if that has any impact hard drive ejection.  The vast majority of complaints do not have anything in common i.e. computers, operating systems (SNL, Lion, and ML), USB 2 or 3 hubs, hard drive brand(s).....My feeling about programs like XtraFinder, although a useful program, may be interfering with remounting of the hard drive(s).  Only a theory though.........

I do not use XtraFinder or any other Finder app.