Generally, a single RPM drive should be able to do more than 80 disk transfers per second. Any higher value needs further investigation. The good thing is, these being real numbers, the number of disks or how they are configured is really not important.
Having more cache on the drive is also important, with many drives now available with 16 or 32 MB built in. It is important to note this is a derived value and not a direct measurement, I recommend reading this article from Mark Friedman, the information still applies to Windows R2.
More exotic interfaces, such as Fibre Channel or SAS tend to be very fast, but also much more expensive. If you ever find yourself analyzing storage performance with Performance Monitor, this post is for you.
To find the disk name to monitor, start Perfmon in Windows. The higher the number the more disk operations are waiting.
When completing an IRP and decrementing the queue depth partition manager will check if the queue depth reaches 0. Disk Queue length value being greater than 1.
Perfmon uses averaging and rounding to keep only meaningful data in its log files, thus allowing captures over a long period of time. Physical Disk Statistics Partition manager partmgr. Regardless of how you choose to set up your storage system, the Performance Monitor counters you use to monitor it will be the same: Why the Performance Monitor?
Total read and write time for all IO requests. The value represents an instantaneous length, not an average over a time interval.
Writes tend to happen very quickly, but if power was interrupted while data was still in the buffer, than that data would be lost. Disk Queue Length counter shows you the average number of read and write requests that were queued on the selected physical disk. A drive letter or mount point mapped to a the representation of a physical disk from an operating system perspective.
Total split IO fragmented IO: There are total 2 write IOs completed since disk counter is enabled, one takes 1 sec and the other takes 2 sec.
For Disk Constraint, enter the value contained within the quotations. Use this information to help with diagnosis. If the disk drive has a sustained load, the value will be consistently high. Therefore, if disk performance is greater than 3 times that amount 15ms or 0.
F represents the frequency of the ticks. Status Details Description Current Queue Number of requests outstanding on the disk at the time the performance data is collected, including requests in service at the time of the snapshot.
Average Queue Average number of both read and write requests that were queued for the selected disk during the sample interval. How to track disk performance?
Is this too much? Note we only track completed IOs here. Total read and write count:Mar 20, · If the disk queue length is the number of outstanding requests that it has not yet been able to pass on to the (virtual) SCSI controller, then this could be a clear sign of a slow storage from the guests perspective.
PerfGuide: Analyzing Poor Disk Response Times Article History “\PhysicalDisk(*)\Avg. Disk Queue Length” and “\PhysicalDisk(*)\% Disk Time” are great counters to use for initial indicators of disk performance when you know how many physical spindles are behind the LUN.
Check the System Event Logs will for disk read/write failures. For example, in a 6 disk array the Current Disk Queue Length value of 12 means that the queue is 2 per disk There are two more metrics similar to Average Disk Queue Length – Average Disk Read Queue Length and Average Disk Write Queue Length.
The Disk Queue Length service monitors the number of read and write requests outstanding on the disk. Note: Devices running Windows cannot monitor the Disk Queue Length service. Jan 22, · Disk Queue Length: Tracks the number of requests that are queued and waiting for a disk during the sample interval, as well as requests in service.
As a result, this might overstate activity. As a result, this might overstate activity. Disk Queue Length. Average disk queue length. The queue length metric displays the number of outstanding requests (read and write) at any given time.
A high number can indicate that there are not enough disk spindles to service the needs of the application or that the existing storage is too slow to keep up with requests.Download