Storage Distributed Resource Scheduler (DRS) is a feature of VMware’s vSphere that enables intelligent virtual machine (VM) initial placement and load balancing based on storage I/O and capacity within a cluster. Storage DRS is an extension of VMware’s Distributed Resource Scheduler feature, which balances virtual machine workloads based on CPU and memory resource utilization.
Storage DRS, which was introduced with VMware vSphere 5, makes the decision to move a VM from one data store to another and tells Storage vMotion to make the move. It uses a new vCenter Server object called a data store cluster, which is a collection of data stores made up of VMFS-5 volumes logically presented as a cluster. Storage DRS can be enabled per data store cluster or per VM.
Also note: Storage DRS supports Network File System (NFS).