Slow on heavy I/O operations.

[Dieter]

> But what I can't understand - why such non-critical(as it seems to me)
> disk activity, cause 100% busyness for disk?

Others have pointed out the effect of seeking.

It would be very useful if there was a way to nice I/O up or down
the way we can nice CPU usage up or down.  Then non-critical
disk activity could be niced down and not impact critical I/O
so much.