Azure VMware Solution HCX WAN-OPT can be a great help to improve bandwidth and speed performances for your replication and/or vMotion-based migrations.
If you have a dedicated direct connection to your cloud provider then pass your way, HCX-WAN Optimization won’t make any difference.
If like me, you use HCX over VPN or even SD WAN, you will enjoy the network boost provided by HCX WAN-OPT !
Despite the fact that VPN is fully supported by VMware and Azure VMware Solution as a HCX network underlay since version 4.2, I would recommend to only use it for Proof Of Concept or test implementation (that is my case) or as backup link for Azure ExpressRoute (direct private connection to Azure Datacenter)
Here is a link regarding the different network underlay supported by VMware for HCX deployment: HCX Network Underlay Minimum Requirements
A very important point to consider when using HCX WAN-OPT is the MTU size limitation to 1500. This involves to have at least 1 vMotion VMkernel configured with a MTU set to 1500 for your on-premise ESXi hosts. If you try to use vMotion with Jumbo Frame enabled via HCX WAN-OPT, it simply fails (Yes, I tried…).
Since HCX 4.4, a new feature called HCX Transport Analytics has been released, which allows you to test and review the underlay network performance for each Service Mesh uplink network. It is associated to HCX Transport Monitor which provides historical or real-time throughput, latency and loss metrics.
These 2 tools are definitely a great added value to accurately monitor your HCX Transport uplink.
HCX WAN-OPT Testing
I currently have a 1GB site to site VPN connection to Azure and vMotion performances were extremely poor before to deploy HCX WAN-OPT appliance. And to be honest, this was expected because this implementation basically runs a VPN (HCX L2VPN) over a VPN (site to site VPN from on-prem to Azure).
I was literally amazed to see such a performance boost brought by HCX WAN-OPT.
The vMotion migration (from on-prem to Azure VMware Solution) of the same VM used to take 3h05 min against 20 min only with HCX WAN-OPT (9,25x faster)! Not only that, but I also noticed that HCX WAN-OPT appliance was able to use all available VPN bandwidth capacity at its disposal.
Azure VMware Solution HCX WAN-OPT is definitely a must if you want to speed up migration/replication of your VMs and drastically reduce transfer times when using a VPN connection!