VMware DirectPath I/O is the technology that gives a virtual machine (VM) direct access to a physical PCI and PCIe hardware devices on the host by circumventing the hypervisor.
DirectPath I/O improves performance on a VM by decreasing the number of CPU cycles needed to run the ESX/ESXi hypervisor. VMware recommends using DirectPath I/O only with high-priority VMs that require maximum network performance.
There are several caveats to using DirectPath I/O because certain features will be unavailable to the VM, such as vMotion, vSphere HA and vSphere FT.
VMware DirectPath I/O was introduced in vSphere 4.0.