How to limit disk usage (Write/I/O) by application? (NOT space usage)

Question

I'm really annoyed by not being able to do a few jobs at a time even if I have plenty of RAM and CPU left to utilise - so it's the disk usage, for example when I am extracting big archives using WinRAR or other disk-write-hungry stuff.

I want to be able to limit this, let's say to 20%, So WinRAR would only use up to 20% of the write capabilities of my disk which should result in

"no more hangups of my OS and being able to multitask even when the I am unpacking a big archive"

when doing such disk-intensive jobs.

If you know how to limit I/O of a disk by application then this will really help!

My OS: Windows 7 Ultimate x64

I tried setting process affinity and priority, but without luck.

Answer 1

In Process Explorer, in addition to the normal Idle or Low priority level, there is an additional Background level, which says that it has Low I/O and Memory Priority. That should accomplish what you want.

I believe it is available in Vista and above, as Wikipedia suggests that I/O prioritization was added then.

From your comment it looks like you also want to do this from the command line. I'm not sure if that is available in Process Explorer, but PsTools might have something useful in this regard. I know PsExec lets you launch processes with low priority. If not, it shouldn't be too difficult to whip up a command line program or script to set the priority of a running process.