Left and Right Ports Differ in Speed by Nearly Three Times
MakeUseOf reporter Kanika Gogia found that when the same USB flash drive was plugged into the left-side port of a laptop, sequential write speed could reach over 70MB per second, but when plugged into the right-side port it dropped sharply to only 24MB per second, while read speeds on both sides were unaffected, remaining at around 97MB per second. She ran benchmark tests with the disk benchmarking tool CrystalDiskMark, which confirmed the difference, and both ports showed as USB 3.0 SuperSpeed specification.
The Culprit Is the Windows Removal Policy
Further analysis with the detection software USB Device Tree Viewer showed both ports were connected to the same Intel USB controller, ruling out hardware specification differences. In Device Manager, Gogia opened the properties window for the USB flash drive and clicked the Policies tab, finding the left side was set to Better performance while the right side was set to Quick removal, which became the key factor affecting write speed.
Write Caching Boosts Speed but Requires Safe Removal
The Better performance setting enables Windows write caching, where the system temporarily stores data and writes it to the flash drive when idle, thereby improving transfer efficiency, but before unplugging you must click Safely Remove Hardware to ensure data is fully written and avoid file corruption or loss. The Quick removal setting disables write caching, with data written directly to the flash drive, allowing it to be unplugged at any time without safe removal, at the cost of slower write speeds.
Switching the Setting Immediately Restores Speed
When Gogia switched the right-side port from Quick removal to Better performance, sequential write speed immediately increased to 71.96MB per second, almost matching the left side, and dropped back to about 24MB per second when switched back to Quick removal. Since Windows 10 version 1809, Microsoft has changed the default policy for USB flash drives to Quick removal, to allow users to unplug devices at any time. If transfer speeds are abnormally slow, check the policy setting in Device Manager, which may restore expected performance.