Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

External Drive keeps disconnecting

I am connecting an external hard drive to read stored data files from it. I am connecting via USB to one of the terminals on the rear of the Mac Mini. My problem is that after about 5 minutes of using this 'connection' I get a message saying that it has been disconnected. The hard drive is still physically connected and powered up but I can no longer see the icon for the external drive within Finder and in order to be able to go back and read files on the external drive again I need to turn it off and turn it on again. I did not have any problems with the external drive before when using with a PC. Does anyone know the cause?

Mac Mini 2010, Mac OS X (10.6.4)

Posted on Nov 10, 2010 6:41 AM

Reply
82 replies

Nov 14, 2017 7:42 AM in response to Leanne73

I might be a years late but seems people still asking. This is probably a power problem. I ran mac OS X with no problem from a Samsung evo ssd inside a non powered enclosure. Tried upgrading to mac sierra via the external then it always disconnected. I managed to find a way around by copying over files. But once upgraded if doing processor intensive actions like compiling code or installing apps the machine would freeze and die. I noticed it was the drive stopping I install keep drive spinning app. Didn't help. I waited until high sierra for a patch. Then I randomly found here that mac OS' (any version) will disconnect your USB device if it's drawing too much power https://discussions.apple.com/thread/3739129?start=15


A USB 3.0 can only deliver 0.9A a good hard drive would draw more than this, in my case 1.4A. I changed the enclosure to one with external 5V DC power input jack (USB to jack cable costs


You can see this in system profiler, I'm not sure why Apple can't build this protection/logging into the OS, it seems it already detects a low amp and disconnects problem anyway.

Sep 17, 2017 3:51 AM in response to Leanne73

I got this issue after updating my Mac Mini to Sierra 10.12.6. Before that no problems with my 4 connect external HD's. Now 2 of them drop their connection every day.

Those two are of the same brand connected via USB 3 port. In system info it says via the ASMT 1053.
One other WD HD stays connected, it says in sys info under USB 3 Bus via Ext HDD1021...

The one connected via thunderbolt also stays connected.

Who is the culprit?

Nov 21, 2010 10:25 AM in response to Leanne73

To make it clearer, look at Apple menu -> About This Mac -> More Info under Hardware -> USB. This will tell you which USB buses your drive, keyboard, and mouse are sharing. If you are attempting to share a drive on too slow a bus, it may disconnect. It really needs a dedicated bus. For Mac Minis, most of the time, it is better to find a good Firewire hard drive to go with them than use USB.

Dec 6, 2010 11:34 PM in response to Leanne73

I am having exactly the same problem.
I am using an IMAC with two external drives connected. The Freeagent drive that is connected by firewire give exactly the same problem that you have. After waking the computer from a sleep the drive wakes up but within a couple of minutes a message says that I didn't eject the drive correctly. The drive then disconnects but keeps spinning. It is not possible to mount the drive using utilities so the power has to be pulled out, and then turned on from scratch. The drive will then act normally for the new session but will fail the next time that it wakes from sleep. (The other WD external drive, running time machine, is working correctly) I have run first aid on the drive but there seems to be no problem. Needless to say I would be very happy to know how to solve this problem.

Mar 27, 2011 1:18 PM in response to Leanne73

I have a Seagate FreeAgent GoFlex Desk 2TB drive. Connected via the USB 3.0 dock (functioning on the iMac's native USB 2.0 ports), I have had good success and a stable connection -- it functions normally. However, I wanted to leverage the GoFlex capability to use another desktop dock, so I bought the FireWire 800 version. While using it (the only FW800 device), I've been seeing the random disconnects as well. My computer is set not to go to sleep (just the display) and the hard drives are not allowed to spin down ("sleep when possible"). This behavior has been consistent between 10.6.5-10.6.7 updates. The only workaround I've found is to create a and run a shell script in the background:
#!/bin/sh
+while true+
do
+touch /Volumes/2TB/touchy.log+
+sleep 600+
done
Basically, the script just generates a minimum of disk activity on a repeating basis. This seems to defeat whatever is timing out on the FireWire 800 bus and causing the disconnections. I've tried this at varying intervals, from every 30 sec. on up to the current 10 minutes and it seems to provide a stable connection to the drive. However, I don't like the "insomniac" nature of a continually spinning disk -- both for energy consumption and for drive wear that will shorten its lifespan. I would like to see this fixed properly, hopefully with the next 10.6 update.

Jun 26, 2011 6:59 PM in response to gperetz

gperetz wrote:


This issue is still present in 10.6.8 after applying the Combo update. Can any Lion beta testers confirm whether it appears to be fixed in 10.7?


If there are any beta testers, they are bound by an NDA (Non Disclosure Agreement); so you will not get an answer to that question: either we don't know or aren't allowed to discuss it.

Jul 31, 2011 2:43 AM in response to gperetz

Problem is still there for me I'm afraid.


I've got the same problem occuring with two different external drives, and it doesn't seem to matter what the connection method is either. I can connect either drive via USB2 or FW800 and the same issue occurs. It will disconnect randomly.


I've considered getting another new drive just for backups but at the moment I can't have any confidence that it will actually connect so I'm rather stuck as to what to do..

External Drive keeps disconnecting

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple ID.