Harddrive speed limits / needs Autopsy Windows

Hi everyone!

Anyone here who can explain more about the neccesary harddrive speeds?
When reading in a new case (for example 250Gb Hardrive image) there’s the source drive.

But Autopsy also needs a evidence folder. Placing them on the same drive will effect the read speed for sure. What’s the most important part for the examining process? The source drive or the drive for the results folder?