Windows
There are numerous advantages to an agentless approach – among them, the ability to quickly capture data from a target without having to schedule the installation of an Acquire.  athene® can process data from Windows and from VMware without having to install an Acquire on either of those operating environments.
Windows performance data can be transferred via Windows Management Instrumentation (WMI), an implementation of Web-Based Enterprise Management (WBEM).  WMI is a core Windows management technology – the “instrumentation” refers to the fact that WMI can get information about the internal state of Windows systems, including the performance objects that can also be retrieved with an athene® Acquire.
Advantages to using WMI include the ability to quickly incorporate a new (or newly critical system) in the athene® database without having to schedule an installation of an Acquire.   Also, many organizations will not allow the installation of an agent on a target system and using this agentless approach will satisfy both the needs of the capacity manager as well as the security requirements placed by the system administrator or security manager.

VMware
VMware stores a complete set of performance data (at multiple levels – datacenter, cluster, resource pool, host, VM) in the vCenter database.  However, the most granular data is only stored in the vCenter database for a short period of time before it’s summarized and/or aggregated, making it less useful to the capacity manager and performance analyst.  Likely, data from months earlier is not available at all, making long term trending and historical analysis and planning impossible. 
Due to the volume of this data and the effect of the size of the database on the performance of the vCenter itself, the VMware administrator is unlikely to keep this granular data for longer periods of time. athene® captures this granular data directly from the vCenter database and securely transfers this data to the central athene® database.  Then the capacity manager can decide how much granular data to keep and how the data will be summarized, aggregated, and deleted from the athene® database. 
No agent is installed anywhere on the vCenter system or anywhere else in the VMware infrastructure.