I have an external hard drive (Western Digital Red 3 TB, WDC WD30EFRX-68EUZN0) in a USB enclosure. Both the drive and the enclosure support SATA at 6 Gbit/s, and the enclosure is connected via USB super-speed (5000 Mbit/s). I'm copying files using
rsync from my internal hard drive (Western Digital Red 6TB, WDC WD60EFRX-68L), and am getting a transfer speed of around 30 MB/s (240 Mbit/s?).
To me this sounds slow, considering SATA 6 / USB-SS support about 20 times that much?
If it is slow, what can I do to diagnose the problem and improve the speed?
Some additional information in response to @Ale..chenski: The enclosure has the name "Renkforce" printed on it. I think that is an "off-brand", belonging to the local semi-professional IT retailer where I bought it (Conrad.com).
lsusb identifies it as
JMicron Technology Corp. / JMicron USA Technology Corp. JMS567 SATA 6Gb/s bridge
so the chip is "JMS567", but I don't know whether that's good or not. At least it confirms that the bridge is supposed to deliver up to 6Gb/s.
The USB connector on the enclosure is labeled "USB 3.0" and it and the included cable are colored blue, which is the code for USB 3.0. So unless they are committing fraud, it quite clearly is a USB 3 device.
On the computer side it is connected to a blue USB outlet labeled "USB 3.0 / UASB" and the super-speed logo. KDE's KInfoCenter shows it as connected to an xHCI Host Controller with a speed of up to 5000 Mbit/s.