I thought I would cross-post here. Oddly, even though the SB uses PCIe NVMe SSDs, it puts up very low write speeds. The 128GB SSD has even slower write speeds than a hard disk (yes, the old spinning kind). See the unusually slow write speed in NotebookCheck's review. The PM951 uses TLC, according to Anandtech. reddit source And, it's hardware. These PM951 drives are not rated for speed, haha: 128GB PM951 ($1500 Surface Book) Sequential read: 600MB/s Sequential write: 150MB/s Random read: 140K Random write: 37K 256GB PM951 ($1700, $1900, and $2100 Surface Book): Sequential read: 1000MB/s Sequential write: 280MB/s Random read: 250K Random write: 74K 512GB PM951 ($2700 Surface Book): Sequential read: 1050MB/s Sequential write: 560MB/s Random read: 250K Random write: 144K Sure, sequential speed isn't that important, but if you copy files...wow. We just got transported back five years in storage performance. Why, Microsoft?