Enable/disable disk performance counters
In Microsoft Windows NT and 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 and/or Drives Monitor gadget.
Diskperf is included in Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, Windows Server 2008 R2, Windows 7 and Windows 10 so that it can be used to remotely enable or disable physical or logical disk performance counters on computers running Windows 2000.
To enable the logical entities, at the command prompt, type: diskperf -y
Both Logical and Physical Disk Performance counters on this system are now set to start at boot. In Windows 10 no reboot is required.
The most useful counters for identifying disk bottlenecks are LogicalDisk\Avg Disk Queue Length and PhysicalDisk\Avg Disk Queue Length. (Read more about Disk Queue Length)These counters display the average number of all requests (read and write) that are queued and waiting to be services for the selected disk. If the queue lengths are more than 2 over a long period of time, this could indicate a disk bottleneck. Actually it generally does if the queue length is not the side-effect of a RAM starved system.
To disable the disk counters use command: diskperf -n
To turn on physical disk counters: diskperf -yd
To turn off physical disk counters: diskperf -nd
To turn on logical disk counters: diskperf -yv
To turn off logical disk counters: diskperf -nv