vSphere storage device latency performance metrics
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vSphere storage device latency performance metrics


Article ID: 309140


Updated On:


VMware vCenter Server VMware vSphere ESXi


This article provides information on storage device latency performance metrics.


VMware VirtualCenter 2.0.x
VMware vCenter Server 4.0.x
VMware vCenter Server 5.1.x
VMware vCenter Server 5.5.x
VMware ESX 4.1.x
VMware vSphere ESXi 6.0
VMware ESXi 3.5.x Embedded
VMware vSphere ESXi 5.5
VMware ESXi 3.5.x Installable
VMware vSphere ESXi 5.1
VMware ESX 4.0.x
VMware vSphere ESXi 5.0
VMware VirtualCenter 2.5.x
VMware ESXi 4.0.x Installable
VMware ESX Server 3.0.x
VMware ESX Server 3.5.x
VMware vCenter Server 4.1.x
VMware vCenter Server 6.0.x
VMware ESXi 4.1.x Embedded
VMware ESXi 4.0.x Embedded
VMware vCenter Server 5.0.x


The vSphere performance metrics made available by esxtop, resxtop and the vSphere Client are averages over the sample timeframe. Measurements snapshots are taken at the end of each sample timeframe and values are averaged. The resulting value reported as the average value within that range.

For more information, see the:

If the sampled metric consists of a non-homogeneous set of data, metrics may be skewed in unexpected ways.

For example:

Measurements of storage device command latency (DAVG/cmd) may generate higher or lower values than expected, if not all commands within the sample complete at the same speed. Most storage device commands complete quickly (< 25ms), but a small number of commands (such as XCOPY, used in VAAI) may take significantly longer to complete.
However, If a particular sample window consists of a low number of fast commands and one very slow command, the average among these are higher than the median.

The measured average of storage latency over a sample window varies significantly depending on how many other commands are completing at the same time, even though these examples depict only a single command which is taking a long time to complete:

  • 4 commands completed in 1ms and 1 command completed in 500ms implies an average latency of 100.8ms.
  • 9 commands completed in 1ms and 1 command completed in 500ms implies an average latency of 50.9ms.
  • 19 commands completed in 1ms and 1 command completed in 500ms implies an average latency of 25.95ms.

Note: Consider what is being measured when evaluating averages of any sampled performance metric before drawing any conclusions based on those metrics.

For more information, see the Performance Analysis Methods Technical Note.

Additional Information

VMware Skyline Health Diagnostics for vSphere - FAQ
vSphere 存储设备延迟性能衡量指标
vSphere ストレージ デバイスの待ち時間のパフォーマンス メトリック
Informações referentes às métricas de desempenho de latência do dispositivo de armazenamento do vSphere