Chapter 1 – VSAN Capacity Planning
As VSAN is a policy-driven storage solution, there is no RAID configuration at the datastore level. All reliability/availability decisions, performance reservations, and so on, are made on a per-VM basis.
Because there is no datastore-level RAID decision being made, VSAN capacity and calculations are based on raw capacity. If you build a VSAN configuration of four nodes with three 2TB HDDs each, the raw capacity of the VSAN datastore will be approximately 24TB.
Capacity will be consumed according to the availability policy specified for each VM. The most typical case is a per-VM mirror. This means that, for the vast majority of all VMs running on VSAN, the datastore usage will be double that of the VM's capacity requirement.
By default, VMs on VSAN are thin-provisioned. You can choose thick-provisioning on a sliding-scale basis (from 0 percent thick to 100 percent thick), and your policy decisions here will also affect the datastore consumption...
