PerfMon Reports Activity On Only One Drive in a FT Set

 Last reviewed: May 14, 1997
Article ID: Q110846
The information in this article applies to:
  • Microsoft Windows NT operating system version 3.1
  • Microsoft Windows NT Advanced Server version 3.1

SUMMARY

Performance Monitor reports activity on only one physical disk in a fault tolerance set. This is expected behavior and occurs because DISKPERF.SYS (the disk performance statistics driver) is located above FTDISK.SYS (fault tolerant disk driver) in the driver stack. For example: 

   file system driver -> disk performance statistics driver ->
   fault tolerant disk driver -> disk driver -> actual physical disks
The decision as to which physical disk gets the data is made by FTDISK.SYS and is therefore invisible to DISKPERF.SYS. Mirrors, stripes, and hardware RAID devices all share this Performance Monitor characteristic: Performance Monitor summarizes all physical disk statistics under the first disk assigned to the disk array.

For more information on monitoring disk performance using Performance Monitor see “Optimizing Windows NT," Volume 3 of the “Windows NT Resource Kit” or query on disk and performance.

Additional query words: prodnt drive harddrive volume
Keywords : kbother ntfault
Version : 3.1
Platform : WINDOWS

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Last reviewed: May 14, 1997
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