If the SSD fails the disk group is associated with is down.  VSAN will operate for another hour and if the drive is not back online or replaced it will begin a rebuild to ensure that the FTT requirements are met.  In the case of a node replacement, obviously it's not an online event for the node you're replacing but the others continue to operate normally. 
Dear expterts,  I have 2 questions about availability.  1. What is the consequence when the SSD disks fails in a node? 2. If one node fails completely, will the replacement be a online event?  Franz
VxRail and availability