VMware Virtual SAN is a new hypervisor-converged, software-defined storage platform that is fully integrated with VMware vSphere. Virtual SAN aggregates locally attached disks of hosts that are members of a vSphere cluster, to create a distributed shared storage solution.

Virtual SAN enables the rapid provisioning of storage within VMware vCenter as part of virtual machine creation and deployment operations.  Virtual SAN is a hybrid disk system that leverages both flash-based devices, to provide optimal performance, and magnetic disks, to provide capacity and persistent data storage. This delivers enterprise performance and a resilient storage platform.

The distributed datastore of Virtual SAN is an object-store file system that leverages the vSphere Storage Policy Based Management (SPBM) framework to deliver application-centric storage services and capabilities that are centrally managed through vSphere virtual machine storage policies.

This 12 page document focuses on the definitions, sizing guidelines, and characteristics of the Virtual SAN distributed datastore.  With the changes and updates recently made to Virtual SAN, there are some significant changes in the recommendation for the sizing of the flash layer.  You should review the below paper as the new sizing guidelines can have an impact on the overall investment and performance of the flash layer for Virtual SAN.

You can download the paper here:  VMware Virtual SAN Design and Sizing Guide