A deeper-dive into Fault Tolerant VMs running on vSAN

After receiving a number of queries about vSphere Fault Tolerance on vSAN over the past couple of weeks, I decided to take a closer look at how Fault Tolerant VMs behave with different vSAN policies. I wanted to take a look at two different policies. The first is when the “failures to tolerate” (commonly referred to as FTT) is set to 0, and the other is when the “failures to tolerate” is set to 1. The question is whether or not we could deploy VMs without any vSAN protection and allow Fault Tolerant VMs to protect them instead.

Supporting Fault Tolerance VMs on vSAN Stretched Cluster

During one of our many discussions at VMworld 2017, I was asked about supporting Fault Tolerance on vSAN Stretched Clusters, more specifically SMP-FT. Now to be clear, we can support SMP-FT on vSAN since version 6.1. The difficulty with supporting SMP-FT on vSAN stretched cluster has always been the possible latency between the data sites, which could be up to as much as 5ms. This is far too high to support SMP-FT on a VM that has data replicating between data sites, and for that reason, we stated categorically that we could not support SMP-FT on VMs deployed on vSAN…

SMP-FT support on Virtual SAN

There have been a number of questions recently about SMP-FT on Virtual SAN. The Symmetric Multi-Processing Fault Tolerance (SMP-FT) is a feature that many VMware customers have been waiting for. With the release of vSphere 6.0, the SMP-FT capability¬† finally became available. This release did not include SMP-FT support when the VM was run on VSAN however. With the release of vSphere 6.0U1, which included VSAN 6.1, there is now support for SMP-FT when the VM is run on VSAN. There are some caveats when it comes to the different VSAN deployment methodologies: On standard VSAN deployments, SMP-FT is supported…