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PostPosted: Sat Aug 19, 2017 6:43 am 
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Between audio recording, backups, storage, Time Machine and start-up clones, I now have six external Glyph Studio Mini drives. I bought a separate 7-port powered USB hub to connect them all to the the computer. I began the process of copying 850+ GB from one drive to a larger one. The Finder began "preparing to copy" and then stopped, but the window stayed open (it never began copying). At the same time, a one-page Microsoft Word document had just been created and I had not saved it.

After waiting several minutes to see if the Finder was going to move forward with the file copying, it appeared that was not going to be the case. I would have to force-quit the Finder. But before I did, I attempted to save the Word document. Word would have none of it. The spinning beachball appeared. I force-quit Word and then the Finder. And then... nothing. After waiting about a minute or so, with no screen action, I shut the Mac mini down with the power button.

When I powered it back up again, just a black screen, however the monitor showed it was getting a signal. Considering what had forced me to shut the mini down that way, I waited a few minutes for the Apple logo. Nothing. Shut down and restarted again, hoping to go into Recovery mode. Again, black screen, no Apple logo. Shut down and restarted again, hoping to boot with a clone. Same story. So now, I'm wondering if I'll be driving to the nearest Apple store and having to buy a new Mac mini.

Then I decided to disconnect all peripherals except the monitor and try again. This put me back on the road to recovery. It seems there's a limit to the number of bus-powered drives one can have on a powered hub... or something. When I re-distributed the USB drive cables between the new hub and the one I already had, I was back in business. I'm still going to put my two all-important audio drives back into the USB ports on the mini itself, as I don't want to finish recording a 30-minute narration and discover the recording failed five minutes into the job.

I'm so glad I had the idea of disconnecting all peripherals before restarting. I could not imagine the mini being blown-up by a forced shutdown.

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PostPosted: Sat Aug 19, 2017 1:23 pm 
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What is the power rating on the adapter for the USB hub? If it's a 7 port hub and is USB 2.0, to power all ports simultaneously the adapter has to provide 0.5A x7 @ 5V, so that would be 3.5A @ 5V for a total of 17.5 watts minimum. For USB 3.0/3.1, it's 0.9A x7, or 6.3A @ 5V. And that doesn't take into account ports labeled with the lightning icon as downstream charging ports using the Battery Charging Standard.

Here's some good reading on that subject.

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PostPosted: Sun Aug 20, 2017 9:07 am 
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I use a hub but I try to keep heavy duty drive use on the built in computer ports on the premise I don't want too much traffic all trying to go over a single USB2 port. For example, right now I have my headless iMac booted off an external drive so I don't want to copy 20GB of data to another drive over the same connection I am using to boot the computer. On the hub I have a flash drive, keyboard and mouse, optical drive (independently powered), analog to digital audio dongle used for an external microphone. Basically intermittent use, low power items. The hub can be used in powered mode but the way I use it I can get away with it unplugged. If I do use the power I think it only supports a total of 2A. I think this is fairly standard for USB2 hubs. I looked at USB3 hubs but they were a lot more pricey and did not operate in an unpowered mode.


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PostPosted: Sun Aug 20, 2017 8:55 pm 
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If you operate a USB2 hub in unpowered mode, it shares 500mA across all ports, and is very easy to saturate and destabilize. No USB hub should ever be used without its accompanying power adapter if it has one. If it doesn't come with one, find another that does.

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PostPosted: Sun Aug 20, 2017 11:56 pm 
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Location: Melbourne
Limnos wrote:
I looked at USB3 hubs but they were a lot more pricey and did not operate in an unpowered mode.

Is this on the your new 'early 2008' you bought recently?
It is good you didn't buy that USB 3 hub as your iMac early 2008 came with USB 2.0 so any USB 3 you plug into it will downgrade to the existing architecture on the board of USB 2.0 which does 480Mbit/s.
I find this fast enough to watch video from a USB plugged-in external drive, but I'd love to have USB 3.0.


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PostPosted: Tue Aug 22, 2017 5:14 pm 
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Tia: the output of the powered USB 3.0 hub with 7 regular ports and 3 charging ports is 12 volts @ 5 amps. For the powered USB 3.0 hub with 7 regular ports only it is 12 volts @ 3 amps. That's the only electrical info I can find, other than the 120 volts AC line current. I use only one of the three charging ports for my iPad, and there are no issues with that. It seems that by connecting my two most relied-upon drives directly into the computer's USB ports, and splitting the remainder of the drives between the two hubs everything is working.

So, either I mistakenly assumed a powered hub would provide the required minimum power at each port regardless of how many ports were in use, or I bought cheesy hubs.

But thanks very much for the information!

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PostPosted: Tue Aug 22, 2017 5:47 pm 
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roam: I bought it when I had my late '08 MacBook so the same issue applied. I know it downgrades to USB2 performance when used with USB2 but my only reason for still buying a USB3 would have been it would work with a newer computer at full speed as and when I owned a USB3 computer. In the end I decided to go with the more affordable USB2 hub since I don't need USB3 right now and when I do most of the things I will use with it still only have low speed demands (optical drive, keyboard, USB2 flash drives).


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PostPosted: Tue Aug 22, 2017 8:50 pm 
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to Limnos,
Thanks for fleshing that out. USB 2.0 is pretty good. As said it can stream video quite well. The instances I would like to use version 3.0 is copying/backing-up GBs of data, and booting into an external OS which takes a while compared even to booting into an OS with Firewire 800 which is much faster. Doing that with USB 3.0 would be faster still and something to look forward to when I get a little more modern.


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PostPosted: Wed Aug 23, 2017 7:32 am 
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roam: I am booting this make-do early 08 iMac off an external right now at USB2. It seems slightly slower than when I used my late 08 MacBook but it also doesn't have the same RAM (4GB vs 8GB in the MB). I am not booted through a hub. Apparently changing drives in an iMac is a matter of completely gutting the computer and I am currently booted off the 1TB 7200 rpm drive I used to have in my MB mounted in a USB3 dock (but the iMac is only USB2 capable). Unfortunately the iMac only has a 250 GB HDD (but it is 7200 rpm) which means I either swap out the drives (not sure which size it takes but I do have a spare 3.5" 1 TB HDD) or I see if I can clone part of the old MB HDD to the iMac and then use one of my 1TB drives to store the bulky stuff (videos, pictures, music). Of course then re-organizing my files and everything too.

Not to threadjack. ;)


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PostPosted: Wed Aug 23, 2017 2:22 pm 
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Its not completely gutting the computer, but it is involved. You have to pull the glass off, then you have to take the LCD out, and then you can access the drive. Once the LCD's out the drive's easily accessible. However there may be thermal management issues with replacing the drive, depending on whether it expects the drive to support thermal monitoring (bad) or whether it uses an external sensor (good).

The retina iMacs are the ones you have to gut, and they're &*(@#&$*( glued together.


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