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Virtual Machine Direct Connect (VMDc) Near native performance with flexibility and data isolation

Virtual Machine Direct Connect (VMDc) enables direct networking I/O assignment to individual virtual machines (VMs). This capability improves overall networking performance and data isolation among VMs and enables live VM migration.

VMDc complies with the Single Root I/O Virtualization (SR-IOV) standard created by the PCI* Special Interest Group (PCI-SIG). Intel played a key role in defining this specification.

The latest Intel® Ethernet server controllers support SR-IOV to virtualize the physical I/O port into multiple virtual I/O ports called Virtual Functions (VFs). Each VF is then assigned to individual VMs to provide near-native networking I/O performance.

SR-IOV provides hardware-based I/O sharing

Dividing physical devices into multiple VFs allows physical I/O devices to deliver near-native I/O performance for VMs. This capability can increase the number of VMs supported per physical host, driving up server consolidation ratios to lower total cost of ownership further.

I/O Virtualization Implementation Models


Intel’s implementation of PCI-SIG SR-IOV uses Intel® Virtualization Technology (Intel® VT) for Directed I/O (Intel® VT-d)Δ to assist the VMM in configuring direct assignment of one or more virtual functions to each VM.

Benefits of a direct I/O assignment implementation

Intel® Ethernet server controllers that support VMDc, in conjunction with support built into VM vendors’ hypervisors, can dramatically improve I/O device sharing among VMs, for higher overall performance:

  • Provides near native performance due to direct connectivity to each VM via Virtual Function (VF)
  • Preserves VM migration
  • Increases VM scalability on a virtualized server
  • Provides data protection via Intel® VT for Directed I/O
  • Supports PCI-SIG SR-IOV standards




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