Product : VMware Inc, VMware Cloud Foundation/v3.0, Enterprise
Feature : Storage QoS, Storage, Infrastructure Services
Content Owner:  Bhagyashri (Shri) Bhagvat
Summary
You can configure the vSAN cluster (shared storage pool) to be either hybrid or all-flash (see details)
Details
You can configure the vSAN cluster (shared storage pool) to be either hybrid where magnetic disks are used for capacity or all-flash where flash disks are used for capacity and then specify clusters from which hosts can use storage

Link to vSAN documentation