disk I/O priorities

[Michael Schwartz]

I notice that when I run a process "niced", only the CPU priority seems
to be effected.  If the process starts heavily accessing the disk and
gets a large number of disk I/O requests into the queue before a higher
prio process runs, the higher prio process gets blocked for a long time
in a disk wait state, suggesting that its disk I/O requests are going
into the queue after the lower prio process' requests.  Does anyone
know if there's a way to prevent this behavior?  Thanks
 - Mike Schwartz
   Dept. of Computer SCience
   U. Colorado - Boulder