Virtual machine storage provisioning historically has imposed operational challenges. Monitoring datastore capacity and I/O load has proven to be very difficult and as a result is often neglected. During the provisioning process for virtual machines virtual disk datastores are often randomly selected leading to hot spots and over- or underutilized datastores – VMware vSphere 5.1 Storage DRS was a new feature introduced in VMware vSphere 5.0 that provides smart virtual machine placement and load-balancing mechanisms based on I/O and space capacity
