VMware Validated Design for Software-Defined Data Center provides alternative guidance for implementing an SDDC that contains two availability zones in the protected region. You use a vSAN stretched management and shared edge and compute clusters to create a second availability zone in Region A to increase their availability because maintenance or loss of one availability zone does not affect the overall operation of the clusters.

In a stretched cluster configuration, both availability zone are active. If either availability zone fails, the virtual machines are restarted in the unaffected availability zone because virtual machine writes occur to both availability zones synchronously. As a result, no data is lost.

Overview of vSAN Stretched Cluster

Virtual machine write operations are performed synchronously across both availability zones. Each availability zones has a copy of the data and witness components are placed on the witness host in Region B. Because the distance between the two availability zones must be minimal, you usually deploy a multi-availability zone SDDC in metropolitan or campus environments.

Extending the management cluster to a vSAN stretched cluster provides the following advantages:

  • Increased availability with minimal downtime and data loss
  • Inter-site load balancing

Using a vSAN stretched cluster for the management components has the following disadvantages:

  • Increased footprint
  • Symmetrical host configuration in the two availability zones
  • Limited distance between the availability zones
  • Additional setup and more complex Day-2 operations
  • License upgrade

Regions and Availability Zones

In the multi-availability zone version of the VMware Validated Design, you have two availability zones in Region A.

Region Availability Zone and Region Identifier Region-Specific Domain Name Region Description
Region A SFO01 sfo01.rainpole.local Availability Zone 1 in San Francisco, CA, USA based data center
Region A SFO02 sfo01.rainpole.local Availability Zone 2 in San Francisco, CA, USA based data center
Region B LAX01 lax01.rainpole.local Los Angeles, CA, USA based data center

Physical Infrastructure

In Availability Zone 2, you apply the same configuration as in Availability Zone 1. You double the hosts for the management cluster and shared edge and compute cluster in Region A, and you place them in the same rack.

Figure 1. Infrastructure Architecture for Two Availability Zones

Component Layout with Two Availability Zones

The management components of the SDDC run in Availability Zone 1. They can be migrated to Availability Zone 2 when an outage or overload occurs in Availability Zone 2.

You can start deploying the SDDC in a single availability zone configuration, and then extend the environment with the second availability zone.

Figure 2. vSphere Logical Cluster Layout with Two Availability Zones

Network Configuration

When using two availability zones, the management VLAN that vCenter Server and other VLAN-backed management virtual machines use must be stretched across both availability zones.

The network between the availability zones must support jumbo frames with latency of less than 5 ms. Use a 10-GbE connection with vSAN for best and predictable performance (IOPS) of the environment.

Figure 3. VMware vSAN Conceptual Network with two Availability Zones