Microsoft RichCopy - Serialize Disk Access?

[+John Teacake MVC]

I'm using Microsoft RichCopy to copy a large amount of data between two USB Hard Disks. As there is a large amount of data I need to get the best possible performance. In the options there is an option that says "Serialize Disk Access" Can anyone explain to me what this is and what it does, How it would affect performance. Should I enable or disable the option or doesn't it make any difference?

[ehlo]

I have no idea but Google shows this which indicates you may get a performance improvement

[xtrabit racing]

Some storage devices are not good at performing simultaneous disk access, such ATA based disk drives especially over the USB. When this option is selected, RichCopy serialize all disk access to the storage, and minimize the overhead at storage device end. This does not mean that RichCopy limits the number of thread running simultaneously.