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Windows Logical Disk
Evaluating Disk Activity
When monitoring logical volumes, they may share a physical disk and the values may reflect contention between them. If you have a spanned, striped, or mirrored volume with disk controllers that support hardware-enabled RAID volumes, the counters report physical disk data for all disks in the stripe or mirror as if they are a single disk. For disks with controllers that use software-enabled RAID, the counters report disk data for each physical disk.
For Windows 2000: By default, the operating system activates only the PhysicalDisk performance counters. Users must activate the LogicalDisk counters manually using the diskperf command.
To use the diskperf command to enable LogicalDisk object counters
At the command prompt, type diskperf – yv
For more information about using the diskperf command, type diskperf – ? at the command prompt.
By default the Windows Server 2003 family, the diskperf configuration is not required
Monitoring: Use the following counters to monitor disk activity.
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WMI Class: Win32_PerfFormattedData_PerfDisk_LogicalDisk [Win2003 only]
Property: % Free Space
Description: Reports the percentage of unallocated disk space to the total usable space on the logical volume. When calculating the _Total instance, the %Free Space counters recalculate the sum as a percentage for each disk.
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WMI Class: Win32_PerfRawData_PerfDisk_LogicalDisk
Property: Free Megabytes
Description: Reports the amount of bytes on the disk that are not allocated.
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WMI Class: Win32_PerfRawData_PerfDisk_LogicalDisk
Property: Avg. Disk Queue Length
Description: 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.
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- Use the % Free Space and Free Megabytes counters to monitor disk space. If the available space is becoming low, run Disk Cleanup in the Disk Properties dialog box, compress the disk, or move some files to other disks.
- If the value of Avg. Disk Queue Length exceeds twice the number of spindles, then you are likely developing a bottleneck. With a volume set, a queue that is never shorter than the number of active physical disks indicates that you are developing a bottleneck. To analyze queue length data further, use Avg. Disk Read Queue Length and Avg. Disk Write Queue Length.
How to monitor Disk Activity using MoniTiL
Prerequisite: Ensure the device to be monitored is in "Monitored Devices"
- Go to "Device Metrics" > "New"
- Template Type: "WMI"
- Template Name: "LogicalDisk FreeBytes"
- Device: select the device to be monitored
- Instance Name: if multiple storage instances exist enter a name to identify the instance, e.g. C:
- Instance: select the instance
- Frequency: use the default, or select an appropriate frequency to query the device
- "Save"
- The Storage is now monitored and a graph will automatically be generated. The graph can be viewed from a daily, weekly, monthly or annual basis to assist in observing trends.
- Alerts can also be set should the "LogicalDisk FreeBytes" fail or threshold exceed a set limit, example if Storage > x units (i.e. > 80% capacity).
- For Win2003/2008, the template "LogicalDisk PercentFreeSpace" can be used.
Reference
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