Why does my external SSD slow down when copying movie image files?

[Tat2sailor]

My OCZ external SSD typically copy files at 300-350mbps but slows down to 180mbps when copying disc image files or .iso Anyone knows why or have a solution? The file does not have a extension so I cannot try changing it & trying out. Thanks!

 

[CountMike]

Large files tend to slow down the transfer because of saturated cache either on disk or RAM.