Welcome to another network related Azure Klouds blog, this time it's all about network acceleration. Acceleration sounds great, it sounds faster and we all need good connectivity, for everything, so what is 'Accelerated Networking' in Azure? Well, to save you time, I've made a list below of the key important things to know about network acceleration in Azure.
Nope, it's not the name of a satellite recently blasted into space, SR-IOV stands for 'Single Root I/O Virtualisation'. Don't worry, we're not going to get into the deep technical detail right now, but it's good to recognise SR-IOV in conversation and associate it with Accelerated Networking.
How does it work? - Network traffic basically bypasses the host (see simplified image below)
What's the advantage? - Reduces network latency, jitter and CPU utilization
I sketched out the image above to illustrate the difference between traditional network traffic and a situation with Accelerated Networking enabled. It's not strictly accurate because there's a layer of hyperthreading that separates the cycles but it usually still touches the CPU but it's a simplistic view of the general idea of acceleration. You might be thinking that it's a real minimal difference but this technology is designed for really traffic heavy, chatty/busy data processing solutions.
The virtual machines that can use Accelerated Networking tend to be more expensive;
VMs with 2+ VCPUs must be D/DSv2 or F/FS SKUs
VMs with 4+ VCPUs must be D/DSv3, E/ESv3, FSv2, LSv2, Ms/MmS, Ms/Mmsv2 SKUs
CPUs behind the VMs/VCPUs must support hyperthreading
VMs must be stopped and deallocated to enable Accelerated Networking
You can have a mix of accelerated and non-accelerated NICs on the same VM
If you have VMs NICs with acceleration enabled and they sit behind an Azure load balancer, make sure it's a Standard SKU load balancer and not Basic SKU if you want to take full advantage of the performance benefits
If you're using a custom VM image for a VM that you want to enable acceleration on it's NIC, make sure you pay close attention to the network drivers in the image to ensure it works
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