> Services > Disk I/O Service

Disk I/O Service

The Disk I/O service monitors read and write operations on the disk.

Devices running Windows 2000 cannot monitor the Disk I/O service.

Service Type

WMI

Instances on a Device

16

Supported Systems/Applications

Any WMI-enabled Server - Windows or workstation

Device Class

Laptop - Windows, Server - Windows, Workstation - Windows

Monitored By

Windows Probes

Scan Interval

15 minutes

Instance

An instance of the WMI class Win32_PerfRawData_PerDisk_PhysicalDisk; for example, _Total.

To find the disk name to monitor, start Perfmon in Windows. Click Add Counters, and in the Performance Object drop-down menus click Physical Disk. The available instances appears in the right hand window under Select instances from list. For Disk Constraint, enter the value contained within the quotations.

You must specify a WSP probe as the monitoring endpoint since this is a WMI service. The device class of the device must be Laptop - Windows, Server - Windows or Workstation - Windows.

Properties Queried and Calculations Performed

Namespace root\cimv2
WMI Class Win32_PerfRawData_PerfDisk_LogicalDisk
WMI Property 0 CurrentDiskQueueLength
WMI Property 1 AvgDiskQueueLength
WMI Property 2 Timestamp_Sys100NS
WMI Property 3 Frequency_Sys100NS
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Status Details

Status Detail

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. The value represents an instantaneous length, not an average over a time interval. Multi-spindle disk devices can have multiple requests active at one time, but other concurrent requests await service. This property may reflect a transitory high or low queue length. If the disk drive has a sustained load, the value will be consistently high. Requests experience delays proportional to the length of the queue minus the number of spindles on the disks. This difference should average less than 2 for good performance.

Average Queue

Average number of both read and write requests that were queued for the selected disk during the sample interval.

Write Operations/Second

The number of write operations performed per second on the selected disk during the sample interval.

Read Operations/Second

The number of read operations performed per second on the selected disk during the sample interval.

Total Operations/Second

The total number of both read and write operations performed per second on the selected disk during the sample interval.

Data Written (KB)

The amount of data (in kilobytes) written to the selected disk during the sample interval.

Data Read (KB)

The amount of data (in kilobytes) read from the selected disk during the sample interval.

Total Data Sent/Received (KB)

The total amount of data (in kilobytes) both read from and written to the selected disk during the sample interval.

Idle Time (%)

The percentage of time during the sample interval in which the selected disk remained in an idle state (all the requests from the operating system to the disk have been completed and there is no pending read or write requests).

Disk Time (%)

The average number of both read and write requests that were queued for the selected disk during the sample interval expressed as a percentage.

Disk Read Time (%)

The average number of read requests that were queued for the selected disk during the sample interval expressed as a percentage.