To prevent possible failures or issues during a vSphere upgrade, which component should be upgraded first?

VMware recommends consolidating and removing all VM snapshots before upgrading vSphere infrastructure because uncommitted snapshot delta files can cause upgrade processes to fail or result in data integrity issues. Pending VM operations must also be completed beforehand, as in-progress tasks may conflict with host-level upgrade operations. Resolving VM state issues first creates a clean baseline for the subsequent infrastructure upgrade steps.

Datastores do not require a separate upgrade step before other components - datastore format updates are handled as part of the ESXi and vCenter upgrade process itself, not as a standalone prerequisite.

ESXi hosts must not be upgraded before vCenter Server - VMware's documented upgrade sequence requires vCenter Server to be upgraded first because an older vCenter cannot manage ESXi hosts running a newer version than itself.

While vCenter Server is the first major infrastructure component upgraded, virtual machine prerequisites such as snapshot removal must be completed before the infrastructure upgrade sequence begins, making VMs the correct first step overall.