Does SoftNAS support VMware vMotion?
Yes, vMotion is a proactive tool for scheduled maintenance and it will may take a while to migrate. The amount of time depends size of the virtual machine (VM) being moved.
Vmware HA (high availability) or FT should use for (fault tolerance) should be used for protection against hardware or infrastructure failure. HA is restarting to another ESX server and FT creates a mirror vm VM in other another ESX host as cluster which gives you zero downtime but does have limit on number of vCPUvCPUs.
For FT, Vmware version 5.x support supports only 1 vCPU. In version 6, Standard and Enterprise supports up to 2 vCPU vCPUs and Enterprise Plus support up to 4 vCPUvCPUs.