With vSphere 4, ESXi supports a direct PCI device connection for virtual machines running on Intel Nehalem platforms. Each virtual machine can connect up to two passthrough devices.

The following features are unavailable for virtual machines configured with VMDirectPath:

VMotion

Hot adding and removing of virtual devices

Suspend and resume

Record and replay

Fault tolerance

High availability

DRS (limited availability; the virtual machine can be part of a cluster, but cannot migrate across hosts)