vSphere 8 vMotion Improvements

vSphere 8 was announced at VMware Explore 2022 in San Francisco. Part of this new major release are vMotion updates. vMotion is extensively developed to support new workloads and is one of the key enablers for VMware’s multi-cloud approach. Whenever a workload is live-migrated between vSphere and/or VMware Cloud infrastructures, vMotion logic is involved.

vMotion over time

vMotion In-App Notifications

With the release of vSphere 7, the vMotion logic was updated to greatly reduce the performance impact on applications during live migrations. Significant work was done to minimize the stun-time, aka the switch-over time, where the last memory pages and checkpoint info are transferred from source to destination. (more…)

Read More

How to Tune vMotion for Lower Migration Times?

In an earlier blog post, The vMotion Process Under the Hood, we went over the vMotion process internals. Now that we understand how vMotion works, lets go over some of the options we have today to lower migration times even further. When enabled, by default, vMotion works beautifully. However, with high bandwidth networks quickly becoming mainstream, what can we do to fully take advantage of 25, 40 or even 100GbE NICs? This blog post goes into details on vMotion tunables and how they can help to optimize the process.

Streams and Threads

To understand how we can tune vMotion performance and thereby lower live-migration times, we first need to understand the concept of vMotion streams. (more…)

Read More

The vMotion Process Under the Hood

The VMware vSphere vMotion feature is one of the most important capabilities in today’s virtual infrastructures. Since its inception in 2002 and the release in 2003, it allows us to migrate the active state of a virtual machines from one physical ESXi host to another.┬áToday, the ability to seamlessly migrate virtual machines is an integral part of nearly every virtualization deployment. The portability of workloads is the foundation for true hybrid cloud experience by being able to move them between on-premises and public clouds using VMware Hybrid Cloud Extension (HCX). vSphere vMotion still is and always will be one of the most momentous game-changers in the IT industry.

A lot has been developed on the vMotion internals over the years to support new technologies.


Read More

ESXi Network Troubleshooting Tools

In the previous post about the ESXi network IOchain we explored the various constructs that belong to the network path. This blog post builds on top of that and focuses on the tools for advanced network troubleshooting and verification. Today, vSphere ESXi is packaged with a extensive toolset that helps you to check connectivity or verify bandwidth availability. Some tools are not only applicable for inside your ESXi box, but also very usable for the physical network components involved in the network paths.

Access to the ESXi shell is a necessity as the commands are executed here. A good starting point for connectivity troubleshooting is the esxtop network view. Also, the esxcli network commandlet provides a lot of information. We also have (vmk)ping, traceroute at our disposal. However, if you are required to dig deeper into an network issue, the following list of tools might help you out:

  • net-stats
  • pktcap-uw
  • nc
  • iperf



Read More

Understanding the ESXi Network IOChain

In this blog post, we go into the trenches of the (Distributed) vSwitch with a focus on vSphere ESXi network IOChain. It is important to understand the core constructs of the vSphere networking layers for i.e. troubleshooting connectivity issues. In a second blog post on this topic, we will look closer into virtual network troubleshoot tooling.


The vSphere ESXi network IOChain is a framework that provides the capability to insert functions into the network data-path regardless of the usage of a vSphere Standard Switch (VSS) or a vSphere Distributed Switch (VDS). The IOChain is a group of functions that provides connectivity between ports and the vSwitch. A port has two IOChains based on the direction to and from the vSwitch. Meaning each port in a set is associated with it an input and an output IOChain. This allows for a modular approach by only including optional elements in an IOChain as configured by the user.

Examples of optional elements in an IOChain are VLAN support, NIC teaming, and traffic shaping. Looking at the high-level components in an ESXi network IOChain, we differentiate between the port group, the vSwitch (VSS or VDS) and the uplink level.

Port group level

This is where an optional configured VLAN is interpreted by the VLAN filter, allowing for VLAN dot1q tags for your port group. The security settings Promiscuous mode, MAC address changes, and Forged transmits are also set at the port group level. The user can also optionally configure traffic shaping, either egress only when using a VSS or bi-directional traffic shaping when using a VDS.

vSwitch (VSS or VDS) level

Incoming packets at the vSwitch level are forwarded to their destination using the forwarding engine. Incoming packets at the vSwitch level are forwarded to their destination using the forwarding engine. The forwarding engine contains port information paired with MAC address information. It’s job is to send the traffic to its proper destination. That can be either a VM residing on the same ESXi host or an external host.

The teaming engine is responsible for balancing network packets over the uplink interfaces. The way it does so is depended on the chosen teaming configuration by the user. The traffic shaper module is added to the IOChain if enabled in the port group level.

Uplink level

At this level, the traffic sent from the vSwitch to an external host finds its way to the driver module. This is where all the hardware offloading is taking place. The Supported hardware offloading features depends strongly on the physical NIC in combination with a specific driver module. Typically supported hardware offloading functions that in NICs are TCP Segment Offload (TSO), Large Receive Offload (LRO) or Checksum Offload (CSO). Network overlay protocol offloading like with VXLAN and Geneve, as used in NSX-v and NSX-T respectively, are widely supported on modern NICs.

Next to hardware offloading, the buffer mechanisms come into play in the Uplink level. I.e., when processing a burst of network packets, ring buffers come into play. Finally, the bits transmit onto the DMA controller to be handled by the CPU and physical NIC onwards to the Ethernet fabric.

Standard vSwitch

The following diagram puts all components together to form the IO chain for vSphere networking using a standard vSwitch: (more…)

Read More