Software virtual switches occupy the host CPU and introduce forwarding delays. SR-IOV allows the virtual machine to directly use the virtual function VF of the physical network card to bypass this layer. This article sorts out the key points of implementing PVE and VMware in three steps: activation, selection, and trade-offs.

Three-piece inspection before start-up

  • Turn on VT-d or IOMMU in the motherboard BIOS, otherwise you will not be able to see the virtual function even after the driver is installed.
  • If iommu=on is enabled in the Linux kernel, PVE needs to modify the GRUB kernel parameters and restart to take effect.
  • After the PF driver is loaded, use the command line to create VFs. The number should be no less than the number of virtual machines planned for passthrough, and confirm that the driver on the virtual machine side is ready.

Selection: The number of chips and ports determines the pass-through capability

When the storage network is used for pass-through, it is recommended to reserve independent network cards to only carry high-performance traffic. Take the models on sale of EB-LINK as an example:PCI-EX8 25G dual optical port fiber optic network card (Intel XXV710 chip)The two optical ports can be connected to two storage switches respectively to form redundancy;PCI-EX16 25G four-port optical fiber network card (Intel E810 chip)It has more ports and is suitable for compact racks with a single card carrying multiple types of traffic. Different VFs are allocated to business and storage to avoid mutual preemption.

Trade-offs after Direct Access

The benefits of VF passthrough are increased throughput and reduced latency, but live migration is usually limited. It is generally recommended that permanent and delay-sensitive virtual machines use passthrough, while ordinary virtual machines still use virtual switches. Before going online, use iperf3 to verify the bandwidth of each VF, and record the correspondence between VF and MAC to facilitate subsequent troubleshooting.

If you are not sure how to calculate the number of VFs and bandwidth when planning the direct-through scale, you can call 0755-83179002 to confirm the configuration list with technical support before placing an order.