https://core.vmware.com/resource/vsan-frequently-asked-questionsCan I use existing SAN and NAS storage in the same cluster as vSAN?
Yes, vSphere can access and use traditional VMFS and NFS datastores alongside vSAN and vSphere Virtual Volumes—all in the same cluster. If your SAN or NAS solution is compatible with vSphere Virtual Volumes, management is easier and more precise as storage policies can be used to manage all of your storage on a per-VM basis.
In most cases, vSphere Storage vMotion can be used to migrate VMs between these various datastore types. This feature makes it easy to migrate existing workloads when there is a need to perform maintenance or retire and older storage solution.