Difference between the disk space statistics mentioned in the vCenter and Aria operations (previously known as vRealize Operations)

Products

• VMware vCenter Server

Issue/Introduction

The output displayed by vCenter using the command df -h and the data shown in Aria Operations metrics differs in numbers. Even though both serve the same purpose of calculating the disk space. 

df -h output on the vCenter :

 

 Output of Aria Operations :

Environment

VMware vCenter 7.0 

VMware vCenter 7.0.x

VMware vCenter 8.0

Resolution

 

df -h:

• This command provides a snapshot of the file system's usage. Shows how much space is used and available on each mount point.
• It reports the space from the host or VM perspective.
• df -h reports a real-time view of space usage, so it's possible that if there is a slight delay between the two tools updating their data.
• df -h reports on the underlying storage (e.g., the ESXi host's local file system or a specific datastore), but it might not fully reflect data aggregated from other layers of the virtualized environment.

 

Aria Operations Metrics:

• Aria Operations collects more detailed performance and capacity data, which includes metrics about the storage systems, clusters, datastores, and more.
• It reports on (e.g., datastore vs. file system) or might include different factors, like overhead, block sizes, or thin provisioning, which df -h may not display.
• Aria Operations might aggregate data over a longer period or use sampling metrics, which can cause slight differences in reported values compared to df -h.
• Aria Operations might pull data for different storage systems or datastores, which could include virtualized storage (e.g., storage policies, vSAN) versus physical disks.