General steps are these:

1.       Put the ESXi host in maintenance mode - Compute 2.       Remove host from vDS switch - Compute 3.       Unmount and detach data LUNs / DO NOT DELETE DATA LUNS - Compute 4.       Remove host from the cluster (Remove from inventory) - Compute 5.       Delete boot LUN for the host, and remove host from the cluster – Storage 6.       Delete the service profile from UCS end - Compute 7.       Remove host from monitoring – SolarWinds 8.       Cleanup IPAM reservation, AD object and DNS reservation – Compute Windows 9.       Mark ESXi as decommissioned in CMDB – SNOW team

There might be some changes based on whether full cluster needs to be decommissioned. In this case, the data luns can be deleted.

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references:

How to properly decommission a VMware ESXi Host - The Tech Journal (stephenwagner.com)

Process in Short: Enter Maintenance Mode Remove Host from vDS Switches Unmount and Detach iSCSI LUNs Move host from cluster to datacenter as standalone host Remove Host from Inventory