The problem I describe is local (U.2 to U.2 SSD on the same machine, drives that could easily performs at 4GB/s read/write, and even when I pool them in RAID0 in arrays that can do 10GB/s).
Windows has weird behaviors for copying. Like if I pool some SAS or NVMe SSD in storage space parity (~RAID5) the performance in CrystalDiskMark is abyssal (~250MB/s) but a windows copy will be stable at about 1GB/s over terabytes of data.
So it seems that whatever they do hurts in certain cases and severely limits the upside as well.
Windows has weird behaviors for copying. Like if I pool some SAS or NVMe SSD in storage space parity (~RAID5) the performance in CrystalDiskMark is abyssal (~250MB/s) but a windows copy will be stable at about 1GB/s over terabytes of data.
So it seems that whatever they do hurts in certain cases and severely limits the upside as well.