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Performance history for virtual hard disks

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This sub-topic of Performance history for Storage Spaces Direct describes in detail the performance history collected for virtual hard disk (VHD) files. Performance history is available for every VHD attached to a running, clustered virtual machine. Performance history is available for both VHD and VHDX formats, however it is not available for Shared VHDX files.

Note

It may take several minutes for collection to begin for newly created or moved VHD files.

Series names and units

These series are collected for every eligible virtual hard disk:

Series Unit
vhd.iops.read per second
vhd.iops.write per second
vhd.iops.total per second
vhd.throughput.read bytes per second
vhd.throughput.write bytes per second
vhd.throughput.total bytes per second
vhd.latency.average seconds
vhd.size.current bytes
vhd.size.maximum bytes

How to interpret

Series How to interpret
vhd.iops.read Number of read operations per second completed by the virtual hard disk.
vhd.iops.write Number of write operations per second completed by the virtual hard disk.
vhd.iops.total Total number of read or write operations per second completed by the virtual hard disk.
vhd.throughput.read Quantity of data read from the virtual hard disk per second.
vhd.throughput.write Quantity of data written to the virtual hard disk per second.
vhd.throughput.total Total quantity of data read from or written to the virtual hard disk per second.
vhd.latency.average Average latency of all operations to or from the virtual hard disk.
vhd.size.current The current file size of the virtual hard disk, if dynamically expanding. If fixed, the series is not collected.
vhd.size.maximum The maximum size of the virtual hard disk, if dynamically expanding. If fixed, the is the size.

Where they come from

The iops.*, throughput.*, and latency.* series are collected from the Hyper-V Virtual Storage Device performance counter set on the server where the virtual machine is running, one instance per VHD or VHDX.

Series Source counter
vhd.iops.read Read Operations/Sec
vhd.iops.write Write Operations/Sec
vhd.iops.total sum of the above
vhd.throughput.read Read Bytes/sec
vhd.throughput.write Write Bytes/sec
vhd.throughput.total sum of the above
vhd.latency.average Latency

Note

Counters are measured over the entire interval, not sampled. For example, if the VHD is inactive for 9 seconds but completes 30 IOs in the 10th second, its vhd.iops.total will be recorded as 3 IOs per second on average during this 10-second interval. This ensures its performance history captures all activity and is robust to noise.

Usage in PowerShell

Use the Get-VHD cmdlet:

Get-VHD <Path> | Get-ClusterPerf

To get the path of every VHD from the virtual machine:

(Get-VM <Name>).HardDrives | Select Path

Note

The Get-VHD cmdlet requires a file path to be provided. It does not support enumeration.

Additional References