I'm using KDE4.3.1 (although this also affected earlier versions of KDE4) on 11.1 and find that when I copy or move large files that my system really becomes sluggish and clicking menu items or opening new apps really lag. I expect some lag but it seems to be abnormal. Is this normal behaviour? I hate drawing these comparisons but it seems to be worse in oS than what I'm used to in XP.

Is there any way to reduce the process priority for moving / copying files cpu and disk? I.E. if I'm copying a large file and then start a new app (or perform any other disk or cpu intensive tasks in the foreground for that matter) then I'd like that to take priority and to slow the copying of the file.