A Microsoft Windows NT and Windows 2000 command for starting and stopping disk performance counters for Performance Monitor (System Monitor in Windows 2000). Counters for the objects Logical Disk (partition) and Physical Disk (drive) are disabled by default because a performance hit of a few percent can occur if they are enabled. You must run the diskperf command prior to monitoring disk activity with Performance Monitor.
On some disk subsystems, enabling these counters might produce a small decrease in system performance, so you should disable them when monitoring of the system is completed. You must reboot the system after running diskperf.
diskperf –n sets the system to not use any disk performance counters.
For the full syntax of this command, type diskperf /? on the command line.