Only run thread when I/O load is low

Question

I have a background thread that performs I/O operations (keeping an index up to date). But in addition to that several clients access the server's hard disk and I want these accesses as fast as possible. So I thought, it would be nice, if the indexing thread is only running when the I/O load is low.

Is there a way to figure this out?

I'm open for alternative suggestions as well.

Answer 1

Use Performance Counters to get the I/O activity of the disks. Once it gets to the low-end of your threshold, allow your threads to run. Don't forget to take into account your own I/O load you'll be adding when deciding what your high-end is for the stopping threshold.

Answer 2

Setting your threads priority to idle should be sufficient.

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Edit

You are right about the fact that the thread's priority does not impact the IO priority.
Take a look at I/O Prioritization in Windows Vista for a detailed explanation.