I have had running two Verbatim 2 TB 3,5" external USB 3.0 devices (http://www.verbatim.com/prod/hard-drives/desktop/store-n-save-usb-3.0-sku-97580/
) and two Revoltec cases (rs078 - Revoltec 3,5" Alu Book Edition 3 black) (http://www.revoltec.net/revoltec.net/index.php?StoryID=7&ArticleID=342&WorldID=4&websiteLang=en
) where I used Samsung 2 TB HD204UI drives for a couple of month at my Qnap TS-459 Pro II system at USB 3.0 ports without any issue.
From my point of view the problems started to show up with the Firmware 3.5.2 builds. After the Firmware was deployed, the USB 3.0 devices don't show up in the Qnap menu when connected at the USB 3.0 port. But if I connect them to the USB 2.0 port, they will show up. Btw. when the USB 3.0 drive is connected and turned on beforehand the NAS starts, the HDDs are still recognized! But when you unplug it and reconnect while the NAS is already turned on, the HDD does not show up as external USB 3.0 device.
Some days ago I installed the latest Firmware 3.6.1 Build 0302T. But the USB 3.0 issue is still there. No hotplug is possible on USB 3.0 ports.
This was the situation till a few days back. Than I started to post at the forum and discussed the issue with a couple of other Qnap users. At the same time I filed an official service request to Qnap.
Right now, the whole USB 3.0 situation has changed again for me.
I was just on the way to start debugging the issue and to get hold of kernel logs etc. than the USB 3.0 ports started to work again!!!
I'm sure I've not
changed anything at the devices or it's configuration. - All my USB 3.0 HDDs are accidentally working again. I can hot plug them as often as I want to, they are always recognized again. Looks like the issue has gone magically!?!?
I will continue to monitor this issue and keep you posted.