The Xiaomi Mi Notebook Pro suffered from less than ideal disk read and write speeds despite having a Samsung PM961 SSD onboard. A BIOS update is now available that enables full x4 bandwidth on the NVMe SSD PCIe lanes, leading to increased read/write speeds.
https://www.notebookcheck.net/Xiaomi-issues-BIOS-fix-for-slow-SSD-performance-in-the-Mi-Notebook-Pro.268266.0.html