I recently purchased an Anker 4-Port Ultra Slim USB 3.0 Data Hub. Two of the devices I wanted to attach to the hub are my OWC Mercury On-the-Go Bus-powered drives (One for Time Machine, one for Super Duper). I have never had any problems of any kind with the OWC drives.

However, when I connect them through the Anker bus, the show begins.

If both drives are connected to the hub, I get a continuous clicky-squeaky sound, as though the drive was failing. If I connect one drive to the hub and the other to my iMac, that sound does not appear…at least, not continuously.

However, once in a while, the drive will make the same sound but as a single strike. Also, without anything being done, the Time Machine drive will periodically think it’s been disconnected and this dialogue box appears.

Disk Not Ejected Properly
Eject “Time Machine” before disconnecting or turning it off.

I assume that means the Hub momentarily stopped providing power to the drive.

If that assumption is correct, is it also safe to assume that the hub just doesn’t have the juice to power either or both drives?

Thoughts?

Do you have the model with the charger? If so, plugging it in will provide more power for the attached devices to draw from. If not, the power that the hub may supply will be in the order of 900 mA for all devices combined, which is about equal to one external hard drive. See respective ratings on each device. If the hub supplies e.g. 890 and the drive wants 910, or more extreme, then you will see power-related errors.

That hub seems nice for thumb drives (sticks), but for multiple hard disks it seems underpowered.

I have the Anker 6-Port, not self-powered (i.e., plug it into an outlet) USB 3.0 Data Hub. It was very highly reviewed, BUT I too have noticed that sometimes it seems to just go off. Most recently some devices I have plugged in to it get picky about in which port on the hub they are plugged. Fortunately the problem is very intermittent, but annoying when it pops up.

Also, it seems your TM backup is an OWC drive. Is it Seagate "spinning rust" (as joemikeb would say)? Mine is a straight Seagate drive, plugged into a USB port on the back of the iMac and every now and then I too get the ejection message you mention. Very quickly it re-mounts itself. I have attributed this to a Seagate problem as it does not happen with any other non-Seagate drives I use.

No....simple bus-powered, which I chose so that I wouldn't have yet another item to find an AC outlet for...and the additional cable clutter.


So, suspicions confirmed.....not enough juice. I guess I should assume that it's also not enough for my only other motorized device, an Apple USB SuperDrive.

Yes, the TM drive is Seagate and the other, for my SuperDuper backup, is HGST....a subsidiary of Western Digital.


I wouldn't be in a hurry to blame mine on the fact that the drive is Seagate, as it's been plugged into the back of my iMac since 2012 without any issues of any kind. The only difference now is that the Mac recently changed from an early 2008 20" iMac 2.66 GHz Core 2 Duo to a 2017 27" 3.4 GHz Intel Core i5.

I've always had good results with Anker products so out of curiosity I looked up the 4 port ultra-slim USB 3.0 Hub with extension cord on their web site and found the following statement:
I think that explains your problem. OWC sells a power supply for their enclosures for $9.75 which could cure the problem.

No such caveat is listed for the Anker 4-Port Ultra Slim USB 3.0 Hub with the 5V/2A dual purpose wall charger. But notice the charger is only 2 amps and a 2.5" 2TB 5400 RPM 2TB Seagate pulls 1.8 Amps in seek or write mode, so even the external power the hub would be marginal for even a single Seagate drive.

Neither HGST or Toshiba drives are as power hungry as Seagate which is why I always buy a bare enclosure and put my own choice of drives in it.

And that is when I started to notice the mysterious ejections with my long-time Seagate—a change to a newer iMac. I think there is some subtle (?) change in the USB voodoo and for some reason Seagate gets weird on occasion. As joemikeb notes, Seagate drives are different in their power requirements.

Could be. I've since plugged both OWC drives into the back of the iMac and I'll see what happens. Not only is the TM drive a Seagate, it's the also the only reasonable monitor as it's the only one "always on". The SuperDuper drive is only fired up weekly to do the full backup.

A data point FWIW: I have an external Seagate HD that I use for CCC backups. It is connected to my iMac (USB 2) via a powered 7 port (USB 3) Anker hub.

Lately, and randomly, CCC would report that the copy failed as the drive could not be found or it was no longer mounted.

Reading this thread may have been my “ah-hah” moment. Even though the hub is powered, it still may not meet the drive’s needs (I know it will not charge my wife’s iPad).

At any rate, I did some cable swapping in hopes that cures my failure issue. I should know in 7-10 days and will then post back my findings.

To clarify, my always on Seagate is not connected via a hub. It is plugged into a USB port on the back of the iMac.

I wonder if OWC is still using Seagate drives in their portable drives which, I would assume, are mostly used in bus-powered mode by people on the road with laptops.

In my case, Seagate is only in my oldest OWC drive. I went to the OWC site and, while they don't provide drive names in the literature, the drive in the picture is an Hitachi.

According to OWC's current specifications the drive in their 5400 RPM 1TB Mercury Elite Pro container is:

By the way at 1.4 Watts this particular western Digital drive uses 22% less power than the bare Western Digitals OWC is offering for sale.

I didn't look at other enclosures or drive capacities but I think OWC pretty much sticks to WD in their populated enclosures, unless the asterisk noted comes into play.