In weak computers, big copy or dd operations slow down the computer substantially. Sometimes one has to wait for 30 seconds until a window will open.
How can I run a big copy with very low priority? I already use
nice -n +15 cp ...
but the renicing of cp has little effect on the resources being taken by copy.
Maybe there is a way to limit a process’s grab on resources or on a hard drive?
I don’t mind if the low-priority copy takes much longer than a simple copy.
Hi
Use ionice - set or get process I/O scheduling class and priority. The man page has examples, but in your case set the cp command to idle…
is it possible to set all the copy processes with lower priority also when I copy dragging and dropping using dolphin??
sometimes opensuse (on a phenom II X4 six processor 2Ghz pc) become nearly unusable when is copying big files… 
You should see no slow down…unless there maybe are bad sectors and it takes multiple tries too read/write them. That can slow things down. Or maybe copying to a USB stick which can pause things to recover deleted sectors.
Run top to see if you can see what is eating CPU.
Thanks.
I tried
ionice -c 3 ....
This helped somewhat. It reduced the delays of starting some programs from 10-20 s to 5-10 s. With computer idle, the delays are 2-5 s.
The biggest effect of ionice: it reduced the longest delays.