VMWare # Many of VMware Admin had faced a situation. VM running on vSAN failed to power on with errors showing insufficient resources and component absent. This occurred after one of the ESXi hosts in the cluster was down for several hours. On investigation we found the root cause. vSAN objects were marked absent because the host holding one replica had been offline for more than 60 minutes. With an FTT=1 policy, quorum requires at least 2 of 3 components. As quorum was lost, the VM could not power on. Steps we performed to resolve the issue: 1. Checked vSAN health using esxcli vsan health cluster list 2. Verified which components were marked absent. 3. Attempted to bring the down host back online as quickly as possible. 4. In case the host is permanently unavailable, we prepared to add a new host and configure a new disk group. 5. Triggered a vSAN rebuild so that missing components could be recreated and quorum restored. 6. Once quorum was available, we retried powering on the VM and it came online successfully. Key takeaway. Always design vSAN clusters with a minimum of 3 hosts when using FTT=1 to ensure quorum and availability.