Use the vSAN Performance dashboard along with the Cluster Capacity dashboard.
How to Use the Dashboard
- Cluster Analysis
The vSAN Clusters widget lists all the vSAN clusters, starting with cluster with the highest VM disk latency. By default, the widget displays data from the last 24 hours.
The first column displays if the distribution of disk latency is experienced by all the VMs in the cluster. You can expect a majority of the VMs to experience latency that matches your expectation.
The second column displays if any of the vSAN kernel modules have to wait for CPU. Expect this number to be near 0% and below 1%, as vSAN should not be waiting for CPU time.
The third column displays if any of the vSAN clusters are dropping packets in the vSAN network (not the VM network). vSAN relies on the network to keep the cluster in-sync. This number should be near 0% and less than 1%.
Select a cluster to investigate further. The VM latency distribution is automatically displayed.
You can view various disk-related contention counters of the cluster from the Contention widget.
Contention metrics are complemented by utilization metrics. A large block size can result in high throughput in a relatively low IOPS. If you see a large block size when you are not expecting it, investigate which applications are using it.
- Disk Groups
You can drill down to the disk group level. All the counters are the worst value among the disk groups.
- Read Cache
All the values displayed are the worst values among the read cache of the disk group.
- Other KPIs
A problem in performance can also be caused by non-storage. vSAN resync is a type of utilization metric, but its presence can impact performance.
- Disk Group Analysis
You can drill down to individual disk groups from the Disk Groups widget. Ensure that the disk groups are fairly balanced. Select the disk group that you want to analyze. Both the contention and utilization metrics are automatically displayed.
- Cache Disks
You can drill down to cache disks from the Cache Disks widget. Ensure that the configuration is consistent. Select the cache disk you want to analyze. Both the contention and utilization metrics are automatically displayed.
- Capacity Disks
You can drill down to capacity disks from the Capacity Disks widget. Ensure that the configuration is consistent. Select the capacity disk you want to analyze. Both the contention and utilization metrics are automatically displayed.