Disk performance counters cannot be collected for virtual machines in a vSAN environment
Article ID: 428570
Updated On:
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Issue/Introduction
Alarms based on counters such as "Virtual machine disk usage (disk.usage.average)" may not be triggered for virtual machines (VMs) residing on vSAN datastores.
The followings are observed:
- Specific disk performance counters (e.g., disk.usage.average) are not displayed or show a value of 0 for VMs on vSAN datastores.
- Disk statistics for target VMs cannot be retrieved using the PowerCLI Get-Stat cmdlet.
- Alarms configured with the above counters do not trigger even when high I/O load is applied to these VMs.
Environment
vSAN (All versions)
Cause
This behavior is a limitation due to the vSAN architecture.
In standard datastores such as VMFS, performance statistics are collected at the SCSI layer of the ESXi storage stack. However, virtual disks (vDisks) on vSAN bypass the SCSI layer and communicate via vSAN-specific protocols. Consequently, values are not reflected in conventional counters like disk.usage.average.
Performance data in vSAN environments is collected and managed separately by the vSAN Performance Service, rather than the standard vSphere performance statistics.
Resolution
To monitor performance or configure alarms for VMs on vSAN datastores, use one of the following alternative methods:
- Monitoring via vSphere Client (GUI)
To monitor the I/O performance for individual VMs, use the following:
Procedure: Select VM in vSphere Client > Monitor tab > vSAN > Performance.
Throughput, IOPS, and latency per virtual disk can be monitored here. - Alternative monitoring tool
Since the conventional "Virtual machine disk usage" alarm does not function, it is recommended to monitor vSAN-specific metrics or use advanced monitoring tools such as VMware Aria Operations (formerly vROps). - Retrieval via PowerCLI / API
Data cannot be retrieved using the standard Get-Stat cmdlet. Use APIs or PowerCLI designed to retrieve internal vSAN performance statistics.
Reference: Mapping vSAN Performance Stats to PowerCLI/API
Additional Information
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