-Question-
What is causing Windows 10 to write data to a USB 3.0 drive at only ~30.0 MB/s?
-Details-
When copying files from an internal desktop SATA3 disk to an external USB 3.0 drive, the write speed is on average about 30.0 MB/s.
-Hypothesis-
It may be possible both the OS and the USB drive have fallen back to USB 2.0 (if so, would there be a way to check if a transfer is actually occurring over USB 3.0. Update: See -Research- below for a method found in another question.)?
Even though Windows 10 is reporting the presence of a USB 3.0 controller, perhaps a problem in the driver is causing a fallback to USB 2.0.
-Research-
A similar issue in Windows 8:
Why can I transfer only 35 MB/s to my USB 3.0 external hard disk?
Determine if a device connected via USB 2.0 or USB 3.0:
Verifying USB connection speed (USB 3 or USB 2?)
-Product Info-
Seagate 1 TB SATA3 Desktop Drive:
http://www.seagate.com/internal-hard-drives/desktop-hard-drives/desktop-hdd/#specs
Seagate 1 TB USB3 Backup Drive:
http://www.seagate.com/products/laptop-mobile-storage/laptop-external-drives/backup-plus-slim/
-System Details-
CPU: Intel Core i7 – Windows 10
RAM: 32 GB
Read Disk: Seagate 1 TB – 7200 RPM – Internal – 3.5 inch – SATA3 – ST1000DM003
Write Disk: Seagate 1 TB – 5400 RPM – External – 2.5 inch – USB 3.0 – STDR1000100
Best Answer
-Simple Answer-
Reboot computer.
-Explanation-
After rebooting system, transfer speed increased to around 100 MB/s, which is optimal for a 2.5 inch external USB 3.0 5400 RPM drive.
It appears Windows 10 loaded a driver for the drive during boot.
-Cause-
Unknown.