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I’m wondering if I have a faulty/weird USB hub.
Whenever my external WD hard drive is connected to this cheap USB hub I own, which happens to have its own power supply, the hard drive will keep spinning on a low speed. The USB hub isn’t even connected to my computer.
The mouse that I have connected to the hub has the same behavior, where it will stay lit no matter if the hub is connected to the computer or not.
Is this the intended behavior of a USB hub? It seems like it unnecessarily keeps the hard drive spinning, potentially reducing its life span.
I don't recall there being a provision in the USB standard requiring devices to auto suspend in the absence of communication. Got a reference? – psusi – 2018-03-05T00:11:47.030
1@psusi, this is by definition. Explicitly, p.150 of USB2.0 specs, "Anytime a device observes no bus activity, it must obey the rules of going into suspend (see Section 7.1.7.6).". – Ale..chenski – 2018-03-05T00:31:26.533
Thank you for your response. I went ahead and purchased a more modern and more expensive USB hub, and while the external HD seems to go to rest when I pull the plug from the computer, the mouse still has its lights turned on. This only happens after the hub has been connected to the computer. Can this behavior stem from how macOS handles USB, or from the mouse itself? – Simon – 2018-03-05T20:42:01.063
Never mind the external HD, it now acts the same problematic way as previously. – Simon – 2018-03-05T20:57:44.590
If you have the hub connected, and PC is soft-down, even a good hub will maintain VBUS power until it gets disconnected or receives USB reset. So the problem of no-suspend is on drive side. Try to disable power management on the hub, it might help to behave differently. – Ale..chenski – 2018-03-05T21:05:04.507
@Simon, more expensive USB hub doesn't necessary mean it has high-side switches on every port. – Ale..chenski – 2018-03-05T21:12:10.577