VMware: Exploring Load Balancing Options

Load balancing is a critical component in any virtualized environment. It ensures that the network traffic is efficiently distributed across multiple paths, optimizing resource use and ensuring high availability and reliability. VMware, as a leader in virtualization, provides several load-balancing policies that work in conjunction with virtual switches. Let’s explore these options in detail and understand their pros and cons.

What is VMware vSwitch?

Before we delve into load balancing, let’s clarify what a vSwitch is. VMware vSwitch, or Virtual Switch, acts like a physical switch within a VMware ESXi host. It enables virtual machines (VMs) on the same host to communicate using the same protocols over physical switches without additional networking hardware.

There are two types of virtual switches in VMware:

1. Standard Virtual Switch (vSwitch): Local to one ESXi host.

2. Distributed Virtual Switch (DvSwitch): Spans multiple ESXi hosts, providing centralized management.

Load Balancing Options in VMware:

1. Route based on the originating virtual port ID

This is the default policy. The virtual switch selects the uplink based on the virtual port where the traffic enters the virtual switch.

  • Pros: Simple, no special requirements, and provides even distribution for a large number of VMs.
  • Cons: Not as effective if the number of VMs is small or if the traffic patterns are uneven.

2. Route based on IP hash

This policy uses a hash algorithm based on each packet’s source and destination IP addresses to determine the traffic’s uplink.

  • Pros: Effective with teamed network adapters and can balance traffic for a small number of high-throughput VMs.
  • Cons: Configuration is complex, requiring configuring the physical switch for EtherChannel or another link aggregation method.

3. Route based on source MAC hash

This option selects an uplink based on hashing the source Ethernet.

  • Pros: Simpler than IP hash and doesn’t require any special physical switch configuration.
  • Cons: Less granular than IP hash and can lead to uneven distribution of VMs have similar MAC addresses.

4. Route based on physical NIC load (Distributed Switch only)

This policy, known as Load-Based Teaming (LBT), dynamically selects an uplink based on the actual load on physical NICs.

  • Pros: Highly efficient, adapts in real-time to network load, and requires no special physical switch configuration.
  • Cons: Available only with Distributed Virtual Switches, which require a higher licensing level.

5. Use explicit failover order

This policy doesn’t perform load balancing but instead specifies the failover order of the uplinks.

  • Pros: Provides control over the order in which uplinks are used.
  • Cons: Does not perform load balancing; primary uplink must fail before others are used.


For Enterprise Class Networks, what typically used?

In large enterprise networks, for example, with over 70,000 end-users, network performance, reliability, and manageability are critical. In such environments, it’s essential to ensure that the network can handle high traffic loads efficiently and scale as the organization grows.

For VMware environments catering to large enterprises with such a significant number of end-users, the recommended choice is to use “Distributed Virtual Switches (DvSwitches)” with the “Route based on physical NIC load” load balancing policy, also known as Load-Based Teaming (LBT). Here’s why:

Scalability: DvSwitches span multiple ESXi hosts, allowing centralized network configuration. This is especially beneficial in large environments with hundreds or thousands of VMs and hosts. It simplifies network management and scales much more effectively compared to standard vSwitches.

Dynamic Load Balancing: LBT dynamically balances the network traffic based on the actual load on physical NICs. In large enterprise networks, traffic patterns can be unpredictable and varied. LBT adapts in real-time, ensuring no network links are overloaded while others are underutilized. This leads to better performance and more efficient use of network resources.

High Availability and Redundancy: Large enterprises cannot afford network downtime. LBT, combined with other network redundancy features of DvSwitches like Network I/O Control, provides better fault tolerance and ensures that the network remains available even if some physical NICs or links fail.

Advanced Monitoring and Troubleshooting: DvSwitches offer advanced monitoring and troubleshooting features. The ability to quickly identify and resolve network issues is crucial in large environments. DvSwitches provide features like NetFlow, Port Mirroring, and Health Check, which are invaluable for maintaining network health in large enterprises.

Centralized Management: With DvSwitches, network configurations can be changed centrally and propagated across all connected ESXi hosts. This is highly advantageous in large enterprises as it reduces the complexity and time involved in managing the network configurations on a per-host basis.

In conclusion, in large enterprise environments with over 70,000 end-users, leveraging the Distributed Virtual Switches combined with the Load-Based Teaming policy is advisable. This combination offers the best mix of performance, scalability, availability, and manageability that large networks require.