Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2VirtualizationMedium
A data center administrator is deploying several virtual machines (VMs) that require high bandwidth and low latency connectivity to storage and other VMs. To optimize performance and reduce CPU overhead on the hypervisor, which type of virtual network interface card (vNIC) should be configured for these critical VMs?
- ASR-IOV vNIC
- BEmulated vNIC
- CPara-virtualized vNIC
- DLegacy vNIC
Show answer & explanationAnswer & explanation
Correct answer: A. SR-IOV vNIC
SR-IOV (Single Root I/O Virtualization) allows a single physical PCIe device to appear as multiple separate physical devices to various virtual machines, bypassing the hypervisor for direct I/O access, which significantly reduces CPU overhead and improves network performance.
Why the other options are wrong
- B. Emulated vNICs provide basic functionality but have high CPU overhead due to full software emulation.
- C. Para-virtualized vNICs improve performance over emulated ones by using hypervisor-aware drivers but still involve hypervisor intervention.
- D. Legacy vNICs are typically emulated and offer the lowest performance.
SR-IOV
Single Root I/O Virtualization (SR-IOV) is a PCI Express (PCIe) standard that allows a single PCIe physical function (PF) to be shared among multiple virtual machines (VMs) as virtual functions (VFs), providing direct hardware access for improved I/O performance and reduced CPU overhead.
- Bypasses hypervisor for I/O.
- Provides near-native performance.
- Reduces CPU utilization on the hypervisor.
Memory trick: Speedy SR-IOV Slices, Hypervisor's Headache Solved.