Have Modbook Pro with OS 10.10.2 and a powered seven-port USB hub. A 750-GB bus-powered drive has no problems with the hub in-between. But a powered drive with three partitions, one of them a Time Machine partition, always gets a failure in backup. Works fine when the hub is not between.
I have 4 USB 3 drives plugged into my MBP via a powered USB 3 hub and two of them have multiple partitions and different filesystems and all work just fine however the Modbook Pro does not yet support OS X 10.10, so that may be an issue.
From Modbook Support Center:
OS X Yosemite Not Currently Supported on the Modbook Pro The newest version of the OS X operating system, Yosemite (OS X 10.10), is not fully supported on the Modbook Pro.
We do not recommend upgrading your Modbook Pro to Yosemite at this time. (Both OS X 10.8 Mountain Lion and 10.9 Mavericks are supported on the Modbook Pro.)
An update to the Modbook Pro System Software and the Modbook Pro Pen Tablet Software offering compatibility with Yosemite and other features will be available in the near future. Check back here occasionally for updates.