Any Problem Using Two External USB-Powered HDDs on rMBP?

Started Mar 29, 2013 | Discussions thread
RustierOne
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Un-mounted Drives Drawing Power in Sleep-Mode
In reply to Najinsky, Apr 13, 2013

Najinsky wrote:

Steve Jobs wrote an article about Adobe Flash in which he claimed it was the number one reason why Macs crashed. I haven't seen any actual figures on it, but my bet would be that the number 2 reason is USB.

It shouldn't be happening like that, but rather than spend a lot of time hunting down the problem, it might be simpler just to install Jettison from the App store for $1.99. This intercepts sleep mode, ejects any external drives, and re-mounts them on wake-up.

As to the cause of the problem:

In sleep mode, the ports should still be supplying power so the drives should remain mounted. This would be important it you were using the Power Nap feature to do Time Machine Backups while the computer sleeps.

Using Jettison seems to have solved the problem of ejecting both HDDs when entering or returning from sleep mode.

But one thing is still troubling. When in sleep mode, both USB ports are still supplying power to the HDDs. So while the rMBP is asleep, the drives are still drawing power from the battery, unless I keep the mains power connected. Both drives, although ejected, still have their power lights on.

So I turned off "Enable Power Nap While on Battery Power" in Energy Saver settings, thinking that was the reason. Nope. It's still supplying power to both HDDs. Sometimes immediately after entering sleep mode (by closing the cover), the OWC 750 GB HDD continues to spin for quite some time. Now this is the case when Time Machine has already finished its hourly backup to one or the other of the drives. Its between the hourly backup cycle, so both drives should be idle.

While it would be easy to just keep the mains connection always plugged in, Apple recommends against having the battery always on charge.

So I just unplug both drives to disconnect them from battery power after going to sleep. But I'd rather not have to always do that, if for nothing more than wear and tear on the USB connections, let alone the extra hassle. If I leave the drives plugged in while on battery power overnight, when it comes out of sleep mode, the state of charge of the battery is significantly reduced - like from 100% down to 85%.

Any suggestions?

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Best Regards,
Russ

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