External Drive UNMOUNTING On Its Own...

Last week I upgraded to Mountain Lion. 2 days ago my 2TB External Seagate unceimoniously unmounted itself - not a seep issue... in fact I often run the comuter for days on end without putting it to sleep or turning it off. I have never had such a problem till now.

Upon rebooting the drive does not mount. If I unplug the drive and reconneect it, it'll mount for a few minutes then unmount generating the error message 'the drive has been improperly disconnected....'

Cable and port switching did not help

Meanwhile I have a FW800 Seagate drive which operates flawlessly.

Read in another thread about usb drier failure - if that's the issue why do my non hard drive peripherals work?

Also should I consider reverting to Snow Leopard?

Have had the same problem starting with SL that my mid 2011 iMac was delivered with. It has persisted with Lion and now ML. It is extremely capricious and sporadic, sometimes going for a week or so with no unmounting and other times it will happen several times a day.

My only external HD is used for Time Machine and just yesterday I put a 1TB drive in the external dock to replace the 500GB . So far, all is well but it will have to go several weeks w/o unmounting before I can conclude that it was a HD issue. I doubt it.

This has been an issue with Apple far longer than I have been a user. I anxiously wait for every new iteration of OS X for Apple to fix it, but no joy yet! It's about time.

My external LaCie is 100% reliable as long as Time Machine is not on. I can use Back Up Now to do new backups and that's fine too. I can also Enter Time Machine.

But if I turn Time Machine on for it to automatically do backups, the external drive will be dismounted after the next Time Machine backup.

It's hard to convince me that this is not a significant Time Machine bug.

What is even more telling, IMHO, is that I have a 2 TB Seagate hard drive partitioned into 4 partitions, one being my Time Machine backup. I regularly observe that partition, and only that partition, dismount itself; the others remain successfully mounted. The only difference is I never get a dialog box stating my drive was unmounted incorrectly, it just dismounts. And if I open Disk Utility it is there and unmounted; if I right click on it and choose mount, it mounts fine. It only seems to happen when the computer goes to "sleep", I have my energy preferences set to only put the display to sleep, not the computer or hard drives. I am running Mountain Lion; unfortunately I don't remember exactly when this issue started as it's not too difficult to resolve.

I am experiencing the same issues with my MBA (mid 2012) and ML. Bought an LaCie 3T usb3 disk as a backup disk for Time Machine. After some time the drive unmounts itself leaving me with a warning message. I haven't figured out yet if it's caused by automatic Time Machine backups as mentioned above, but I will look into it.

Another issue with this disk is that sometimes it isn't detected properly when plugged in. It doesn't even show up in the 'System Information' usb section and won't 'spin up'. So I first thought those two issues might be connected with the disk's own controller beeing faulty.

I already switched power and usb-cable but the problem persists.

Does anyone else had these specific kind of problems with an external hard drive (i.e. not spinning up and being detected) and OS X?

Currently I have plugged it into my Linux laptop and it seems to work fine.

i, as everyone else, have been experiencing these issues every now and again so here's my revised list of reasons:

1] the USB cable. by far the most common cause.

2] power supply to the box. some drives are hungrier than others. if the external box has its own power supply, the power supply and/or cable to the box

3] the external drive overheating. I'm seeing this very often. Change the cooling of the box, or the drive itself.

4] connections inside the external drive being loose. Lacie "little disk" drives by Sam Hecht do that.

5] the external drive having an automatic sleep function that prevents it from working well with OSX. This should not be high up on your list of probabilities but it does happen. 3.5" WD Caviar Green-s are well known for this, and I'm seeing a Hitachi Deskstar 7200 with the same trouble. Basically OSX times out waiting for the drive to spin back up.

6] and of course, software bugs. OSX is full of them.

If you run out of options or are simply annoyed by the spin-up-spin-down cycles, you can have your drive kept alive by a simple script. I'll leave you to find out how. Don't ask me how. I googled it.

Hello Everyone,

I've been reading and googling for the past couple of hours with no real solutions. I've read every post so far in this thread and I will now contribute my details:

1) MBP 2.33 Intel Core 2 Duo running 10.6.8

2) I never use Time Machine. (I use my own rsync scripts)

3) I have never set the hard drives to sleep. In fact, the computer doesn't sleep unless its on battery power.

4) I have a total of 8 G-Drives that I've purchased at various times over the past few years.

5) I always daisy chain my G-Drives on the FW800 port.

6) I have never had this problem until now, with my newest 2TB G-Drive w/FW800 and USB 3.0

7) I have tried various combinations of cables and power supplies.

The older model G-Drives still work fine but the newer one unmounts randomly, sometimes within 5 minutes. I'm going to take the drive back to the Apple store and exchange it. I'll let you know what happens.

Reading back through all of the replies, I cannot see a common denominator. It doesn't seem to be brand of drive, port type, cable, OS version, or anything else. Was some new energy saving spec added to hard drive manufacturing in the past year or two? Is it drives that have USB 3.0 and FW800?

I also have G-Drives like you. Four of them daisy chained with firewire 800, and mine would dismount everyday when it slept. Now that I have the computer in never sleep mode I never loose my hard drives.

Mountain Lion 10.8.3

Exchanged my G-Drive yesterday. I plugged it in by itself and it worked fine.

Next, I daisy chained it with one of my older 2TB G-Drives, the older drive being the first drive on the chain. The new drive dismounted after about 10 minutes with the all-too-familiar warning message about properly disconnecting your drive.

Next, I switched the order of the chain, with the new drive being first. They both came up and I left them running all night. No problems.

Just weird.

The two G-Drives are both 2TB with USB 3.0 ports. They look identical in every way. However, they make distinctly different sounds when starting up. I bought the older one about a year ago.

The only difference I can see, is on the sticker on the underside of the drives. The older one says "Made in China" while the newer one says, "Assembled in China with components from Thailand".

I just got a usb 3.0 external case to put my 2TB Western Digital drive in it. The drive was in my FireWire enclosure that had a fan. The usb case didn't have a fan. After one day in the usb case my volume kept on unmounting. I took the case back and got one with a fan and the problem stopped. I don't know if the WD drive was causing the unmounting or the usb circuit board in the case was having the problem. I'm just glad for this thread because I thought it was maybe a bad usb port on my new iMac 27.

Another "me too" -- I have a USB 3.0 LaCie Rugged Key -- 32GB version...it gets really hot then it will disconnect randomly, only when using it on my MBP 13" retina. On my PC, it's fine.

well,

i'm on a macbookpro mid 2010, on snow leopard, with an external firewire 800 G-Tech G-RAID 2Tb, i use it as a backup and to work with logic and FCP (i have all my sounds on it) and everything was working fine so far;

a few weeks ago it begun to unmount by itself with error messages, and it's going from bad to worse.

i contacted G-Tech who told me that it's because it's raid1 and it needs to be in raid0 instead, but if so, why did it work perfectly before and now it's a mess ?

and this happen even with "put the hard drive to sleep when possible" unchecked.

i'l try with the computer on "no sleep mode" to see what and if it does something, but i think my next move will be to ask for a replacement since it's still under warranty.

Guess I should update everyone -- LaCie sent me a new USB 3.0 Rugged Key. This one actually works and doesn't unmount on its own. So problem solved. It was the storage, not the mac.

Adding my voice to the multitude. I’ve been working with my wife’s Macbook Air for about two months on an issue similar to what everyone else is describing.

TL;DR: We’ve gone through three different hard drives from different manufacturerers trying to diagnose the issue – all three have exhibited the same problem. I’ve isolated the the account, the cables, and the location of the computer (for environmental factors like overheating). I’ve determined the disconnect is triggered by an automatic Time Machine backups – turning TM off and using a manual “Back Up Now” does not trigger a disconnect. Have not been able to determine the exact cause, whether it’s the drive, TM, or the combo.

Longer version: My wife has a mid–2011 Macbook Air. She has two external drives: one for Time Machine, one for large media (iTunes, iPhoto). We have an encrypted Time Machine back up both the Air’s internal hard drive and the external media. About 2–3 months ago, the media drive started to unmount itself.

1. The first media drive we used was an old 500GB Maxtor drive I’d purchased about 4 years ago. I scanned the drive several times. There was no indication of failure other than this unmounting issue. I tested different cables and it still occurred. I tested different USB ports and it still occured. Since the possibiliy of drive failure was high, I copied everything over to a second hard drive. Eventually the Maxtor did die, so I felt confident it had just been at the end of its life.

   
   

2. The second hard drive was also an older drive, a 250GB Hitatchi laptop drive that used to live inside my Macbook Pro. (I took the Hitatchi out after I replaced it with a different drive.) I put this in a Thermaltake hard drive “toaster” that serves as an external enclosure. We again used this drive to host media. The drive started unmounting itself again during normal operation.

   
   

   I started doing more intense testing. I created a new user account and observed the Hitatchi drive continue to unmount. I eventually identified the trigger, if not source, of the problem: an automatic Time Machine backup would cause the drive to unmount. If I performed a manual backup, the drive would remain mounted. I started to copy console messages and google them, often finding them associated with drive errors and Time Machine. I found it hard to believe that a second drive would fail on me so soon after the first, so I did scans in Disk Utility and DiskWarrior. I found no errors. For good measure, I rebuilt the drive index using DiskWarrior, just to make sure there wasn’t any corruption there. I continued to observe the drive unmounting on automatic Time Machine backups. I made sure the drive was fully exposed to air, still saw the issues.

   
   

3. Convinced it must either be the drive or the Air’s software or hardware, I decided to purchase a new drive. This was a 1TB USB 3.0 Seagate 1.8" external drive. Because this drive was so much larger than the Time Machine backup, I swapped the two: the smaller drive which had been for Time Machine now contained media, and the 1TB Seagate now contained a brand-new Time Machine backup. I performed the initial backup with no issues. A day or so later, we noticed the Seagate – now the Time Machine backup, not the media drive – had been unmounted. Later testing confirmed it happened on automatic Time Machine backups.

   
   

At this point, I’m not sure what to do. I’m considering returning the Seagate and getting another drive, possibly another Seagate, but probably a different brand just to be sure. From my experience so far, something’s clearly not getting along between Time Machine, certian backup behaviors such as backing up data from an external drive, and certain drive models or chipsets.