I've started the system data collection sets, and they've been active for a
few weeks now.
But when I look into the table snapshots.performance_counter_values and
select the records which correspond to the instances
object_name='LogicalDisk' and counter_name='% Disk Time' I retrieve some
records which have values up to 700.

Can someone explain this.

Hi Franky,

This value is the same as what you would normally see from the system
perfmon counter "% Disk Time" for the LogicalDisk object. This attribute can
sometimes have a value greater than 100% when you have SCSI disks and use
RAID controllers. This is because % Disk Time counter also includes time for
overlapping IO requests and indiciates the queuing time for servicing that IO
request. You should take a look at "Average Disk Queue Length" and "Average
Disk second / {Read | Write | Transfer}", which are much better indicators of
your unlying storage subsystem performance.

Also refer to this excellent Performance Tuning Guideline for Win2k8,
http://www.microsoft.com/whdc/system...f_tun_srv.mspx (take a look
at the secion on "Performance Tuning for Storage Subsystem").

"Franky" wrote: