SII was a product that acted as a simplified version of SAI + Splunk Enterprise. It lacked features like access to Search & Reporting and more granular control of Splunk for users who didn't want to jump right into the complexity of Splunk Enterprise. Most importantly, it's a deprecated product. Going forward, users should use SAI to receive the latest features and updates.
SAI works for both physical and virtual environments. How your resources are displayed depends on how you send data from entities to SAI. For example, based on your configuration, you can discover an AWS server as a standalone Linux server, as part of a larger AWS infrastructure, or as both. As of version 1.4.0, SAI has no support for integrating with VMware directly. However, this may change in the next major release. 😉 Stay tuned.
Splunk App for VMware and Splunk App for Infrastructure have different features. They're more complimentary rather than one being strictly better than the other.
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