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What does 'Highest active time' for disk activity in Windows resource monitor mean?

What does 'Highest active time' for disk activity in Windows resource monitor mean?

I know what the disk io, disk queue length and other measures are, but what does 'Highest active time' mean?

Asked by: Guest | Views: 53
Total answers/comments: 2
Guest [Entry]

"I’m pretty sure it is the same as the Perfmon counter ""PhysicalDisk _Total %time"". (It tracks this counter in lock-step.)

Perfmon gives this description of that counter:

% Disk Time is the percentage of elapsed time that the selected disk drive was busy servicing read or write requests.

Basically, it is the percentage of elapsed time that the physical drive(s) were busy. So Even though your MB/s usage may be low, the % busy time can be high if the disk is heavily fragmented, or is otherwise thrashing on lots of small operations.

On a server where you would try to match the right level of high-performing disks to the workload, you would consider the disk subsystem to be a potential bottleneck if the % active (busy) time plateau-ed above 80%. On a workstation if this number is high, it just tells you that your disk performance is maybe what is slowing down your work.

As to your last question: I'm quite certain it is the physical disk and not any kernel or process time. While waiting on the physical diskthe kernel blocks whatever processes is waiting on that disk operation, and uses the CPU for whatever else needs doing."
Guest [Entry]

"From Mahalo:

The highest active time is the
percentage of time spent performing IO
(actually processing time spent at the
IO level). It can get to 100% if Vista
is defragmenting or doing some other
IO heavy operation and very little
else is going on."