What is SR-IOV technology and why we need it

Last updated on March 2, 2020

Dear Friends in this tutorial we will see what it SR-IOV technology and why we need it? So let’s start and see. First of all we will see What is SR-IOV?

What is SR-IOV Technology?

The SR-IOV technology is a hardware-based virtualization solution which improves both performance and scalability. It’s standard enables efficient sharing of PCIe (Peripheral Component Interconnect) express devices between virtual machines and is implemented in the hardware to achieve input output (I/O) performance which is comparable to native performance.

SR-IOV specification defines a new standard wherein the new devices that are created will enable the virtual machine to be directly connected to the I/O device.


A single I/O resource can be shared by many virtual machines. The shared devices will provide dedicated resources and utilize shared common resources. In this way, each virtual machine will have access to unique resources. Therefore, a PCIe device, such as an Ethernet Port, that is SR-IOV enabled with appropriate hardware and Operating System support can appear as multiple, separate physical devices, each device with its own configuration space.

These are two types of function in SR-IOV Technology.

  1. Physical Function (PF)
  2. Virtual Function (VF)

Physical Function (PF): – A PCI Function that supports the SR-IOV capabilities as defined in SR-IOV specification. A Physical Function contains the SR-IOV capability structure and is used to manage the SR-IOV functionality. PFs are fully featured PCIe functions that can be discovered, managed, and manipulated as like any other PCIe device. PFs have also full configuration resources, and it can be used to configure or control the PCIe device.

Virtual Function (VF): – A function that is associated with a Physical Function. A Virtual Function is a lightweight PCIe function that shares one or more physical resources with the Physical Function and with other Virtual Functions that are associated with the same Physical Function. Virtual Functions are only allowed to have configuration resources for its own behavior.

For mode details about SR-IOV you can Click Here

Benefits of SR-IOV

The SR-IOV standard allows efficient sharing of PCIe devices among IO Guest Domains. An SR-IOV device can have hundreds of Virtual Functions (VFs) associating with a Physical Function (PF). The creation of VFs can be dynamically controlled by the PF through registers designed to turn on the SR-IOV capability. By default, the SR-IOV capability is turned off on the server, and the PF behaves as traditional PCIe device.

  1. Performance: – Direct access to hardware from virtual machines environment.
  2. Cost Reduction: – Capital and operational expenditure savings include
  3. Power savings
  4. Reduced adapter count
  5. Less cabling
  6. Fewer switch ports

So in this tutorial we have seen SR-IOV functionality.

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