A DRS cluster has certain vMotion requirements.
To enable the use of DRS migration recommendations, the hosts in your cluster must be part of a vMotion network. If the hosts are not in the vMotion network, DRS can still make initial placement recommendations.
To be configured for vMotion, each host in the cluster must meet the following requirements:
vMotion does not support raw disks or migration of applications clustered using Microsoft Cluster Service (MSCS).
vMotion requires a private Gigabit Ethernet migration network between all of the vMotion enabled managed hosts. When vMotion is enabled on a managed host, configure a unique network identity object for the managed host and connect it to the private migration network.