I tried all combinations of connecting drives, with and without USB hubs, but still no joy. Finally, I don't know why, I disconnected the Anker 7 way powered USB hub from iMac and power source and voila, all has been working for two days!
I had no problem with the hub for over a year, but it seems it was causing a problem now. I have been using these for years as the powered hub left the drives running continuously, even when the Mac was off. There is no problem with that as everything plugged into these has its own power source.
I can get some work done now, knowing everything is being automatically backed up to my my backup drives. Posted on Dec 29, AM. Page content loaded. I would start by removing one of the 3, 4, or 5 drives and then run for a period of time until I could isolate which drive is causing the problem. I would try a different self-powered Hub. Another option is to only connect up the 3 CCC and 5 SD drives one at a time while your actually doing a backup.
How to recover data from the corrupted/unrecognized external hard drives?
Dec 7, AM. I'm having a similar problem. In most cases, the drive reboots itself fairly quickly, but in one case, I had to pull the power adapter plug from the rear of the drive, wait a coupla minutes and replug, and the drive came back up. I am using a Manhattan 28 port self-powered hub. It's brand new. I bought the Manhattan because the older 10 port hub I was using was doing this same trick, so I know it is not the hub.
One drive My Book 3TB in particular drops out a lot. I swapped the USB cable on this drive, and the problem went away for a while, but now it's back. Mid 27" iMac, MacOS This problem started after I upgraded to the initial version of High Sierra. Dec 7, PM. Dec 8, AM in response to den. All my drives are powered from their own PSU and so don't draw current to drive the disk.
Disconnecting external hard drive | MacRumors Forums
The USB hubs are Anker units. I didn't have this problem until High Sierra, so possibly that is the problem. I wonder if there is a firmware issue between the drives and the iMac. I will try and find what firmware is on the MyBook as that works fine and see if its the same as the Elements. If not maybe I could try changing the firmware on one drive to the same as the MyBook to see if that cures it. The other drive that works all the time was a WD Element, but its closure died and I now run the drive in a caddy as want to upgrade it anyway to a Thunderbolt drive.
Dec 8, AM.
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Dec 8, AM in response to jaigieese In response to jaigieese You seem to have a very similar system and problem. Hold down the Option key, click on the Apple menu, and choose System Information. In this list look for the Current Required mA entry for each device. Something like a printer may require very little power whereas a web cam or media card reader may want the full mA. Some Apple devices such as iPhones and iPads require more than mA at 5 volts so that they can fast charge.
Run through the list and do the math. Asked 4 years, 3 months ago. Active 8 months ago. Viewed 37k times. Any help would be appreciated. Computer system is Mac Pro 3.
FAQ: External USB drives randomly disconnecting…
Ok it seems that you are correct, It is an issue with my USB 3 card. It shuts down essentially when the computer goes to sleep. My solution for now is an application called Jettison for Mac. It safely unmounts drives when the computer goes to sleep. I cant say if it is the best option but I stopped getting the notification, so we will see.
Brian Muntz Brian Muntz 11 1 1 bronze badge.
Devices disconnecting? It's about the hub, bub
This directly contradicts the accepted answer. Could you give some explanation about why the other answer is wrong on this point and you're right? Have the same problem here. This solution does not work. Unchecking "Put hard disks to sleep when possible" in Energy Saver has no effect.
Fish Monitor Fish Monitor 3 3 silver badges 9 9 bronze badges. I switched to and "unswitched" outlet on surge protector and now all is good. Vriens 1, 6 6 gold badges 13 13 silver badges 19 19 bronze badges. Featured on Meta. Feedback post: Moderator review and reinstatement processes.
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