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% Disk Time
Folks, Can someone explain me what is meant by "Percentage Disk Time" please it is one of the performance counter that we are supposed to monitor during our performance testing.
Re: % Disk Time
Disks store programs and the data that programs process. While waiting for a computer to respond, frequently the disk is the bottleneck. In this case, the disk subsystem can be the most important aspect of I/O performance, but problems can be hidden by other factors such as the lack of memory.
Performance Monitor disk counters are available with either the LogicalDisk and PhysicalDisk objects. LogicalDisk monitors logical partitions of physical drives. It is useful to determine which partition is causing the disk activity, possibly indicating the application or service that is generating the requests. PhysicalDisk monitors individual hard disk drives, and is useful for monitoring disk drives as a whole.
The suggestion here is to only do full disk performance monitoring if the Disk Queue Length is medium or high. The impact of full monitoring is significant and could influence other counters and give you inaccurate readings and potentially inaccurate conclusions.
Performance Monitor disk counters are not enabled by default and must be enabled manually.
To activate disk performance statistics on the local computer:
Start a command prompt, and type diskperf -y
Restart the computer.
To activate disk performance on a remote computer called Server1
Start a command prompt, and type diskperf -y \\server1
Restart the remote computer.
If using a RAID implementation, start diskperf with the -ye parameter to get enhanced counters.
Monitor the following Performance Monitor disk subsystem counters:
<LI>% Disk Time: This indicates the amount of time that the disk drive is busy servicing read and write requests. If this is consistently close to 100 percent, the disk is being used very heavily. Monitoring of individual processes will help determine which process or processes are making the majority of the disk requests.
<LI>Disk Queue Length: Indicates the number of pending disk I/O requests for the disk drive. If this value is consistently over two, it indicates congestion. This counter is the single most significant counter that you can use to find out if your server is dealing with disk contention. If disk contention is found then detailed analysis of all the other counters need to be done.
<LI>Avg. Disk Bytes/Transfer: The average number of bytes transferred to or from the disk during write or read operations. The larger the transfer size, the more efficient the system is running.
<LI>Disk Bytes/sec: This is the rate bytes are transferred to or from the disk during write or read operations. The higher the average, the more efficient the system is running. [/list]
Counter Acceptable average range Desire high or low value Action
% Disk Time Under 50% Low Monitor to see if memory paging is occurring. Upgrade disk subsystem.
Disk Queue Length 0-2 Low Upgrade disk subsystem.
Avg. Disk Bytes/Transfer Depends on subsystem High Upgrade disk subsystem.
Disk Bytes/sec Depends on subsystem High Upgrade disk subsystem.
[This message has been edited by rstens (edited 01-06-2003).]