50 MB/s is the fastest I've seen from HDD Raw Copy Tool, through USB, SATA, or from a disk image to physical disk so it's definitely a hard limit. I'm currently averaging 175 MB/s with HDDSuperClone though so thank you KaosEngineer for that one
How to set disk cloning from image in HDDSuperClone?
HDD raw copy TOOL 50 MB/S
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How to set disk cloning from image in HDDSuperClone?