No problems, instead a hardware review that might help.

I use two machines as servers, one acts as an offsite hot
spare for the other.  They have external Seagate USB3 drives
for backups, and connect through PCIe to USB3 interface cards. 

After good luck with a Plugable card that is no longer made,
and bad luck with a BYTECC card that should never have been
made, I ordered a couple of cards from Newegg to see which one
works better with my ancient RHEL 6 linux (2.6.32 kernel) and
mobos.  The winner is a Siig JU-P40212-S1, $30 from Newegg
(on sale? and free shipping - "7 day egg saver" was one day
from so.Cal. to Oregon).  TI chipset, xhci driver.

More information at http://wiki.keithl.com/USB3Test 

Keith

P.S. Yes, I know the Seagate externals are unreliable. 
But they are cheap and 8 watts and fast, and two of them on
separate wall warts is more survivable than an internal drive
sharing the same power supply as a drive I want to back up. 
I plan to power them through a USB-controlled power switch,
so they are powered off and inaccessable and difficult to
hack when I am not actively using one of them at a time,
ping-pong alternate days.  What, me paranoid?

-- 
Keith Lofstrom          [log in to unmask]