Quick Tip - Retrieving vSAN usage & overhead information using vSAN API

Within the vSphere UI, you can view a detailed breakdown of your vSAN storage utilization including various system overhead by selecting a specific vSAN Cluster and then navigating to Monitor->vSAN->Capacity as shown in the screenshot below.

Different vSAN configuration such using vSAN Original Storage Architecture (OSA) or vSAN Express Storage Architecture (ESA) and whether capabilities like vSAN Deduplication and Compression is enabled will yield different utilization metrics that are displayed.

I recently had an inquiry asking how to retrieve the vSAN Deduplication and Compression overhead information using PowerCLI?

While the PowerCLI vSAN cmdlet Get-VsanSpaceUsage does provide a number of the usage metrics shown in the vSphere UI, it does not expose every single property.

However, we can still leverage PowerCLI to retrieve this information by simply using the underlying vSAN API which provides this information and specifically the querySpaceUsage() vSAN API. As you can see from the vSAN API documentation, the API method will return an array of vSAN usage object types, which maps back to what you see within the vSphere UI by decoding the ObjType property.

To demonstrate the use of this vSAN API, I have created an example PowerCLI script called vsanUsageAndOverheadInfo.ps1 which you just need to update the variable $vsanCluster with the name of your desired vSAN Cluster.

After connecting to your vCenter Server, you can simply run the script as shown below:

./vsanUsageAndOverheadInfo.ps1

Here is a screenshot of the output from the script: