For a successful upgrade of your ESXi hosts, understand and prepare for the changes that are involved.

For a successful ESXi upgrade, follow these best practices:

  1. Make sure that you understand the ESXi upgrade process, the effect of that process on your existing deployment, and the preparation required for the upgrade.
  2. Prepare the system for the upgrade.
    • Make sure that the current ESXi version is supported for the upgrade. See Overview of the ESXi Host Upgrade Process.
    • Make sure that the system hardware complies with ESXi requirements. See ESXi Requirements and VMware Compatibility Guide at Check for system compatibility, I/O compatibility with network and host bus adapter (HBA) cards, storage compatibility, and backup software compatibility.
    • Make sure that sufficient disk space is available on the host for the upgrade.
    • If a SAN is connected to the host, detach the Fibre Channel system before continuing with the upgrade. Do not disable HBA cards in the BIOS.
  3. Back up the host before performing an upgrade. If the upgrade fails, you can restore the host.
  4. If you are using Auto Deploy to provision hosts, the user who is running the process must have local administrator privileges on the ESXi host that is being provisioned. By default the installation process has these privileges and certificate provisioning happens as expected. However, if you are using another method than the installer, you must run it as a user who has the local administrator privileges.
  5. Depending on the upgrade option you choose, you might need to migrate or power off all virtual machines on the host. See the instructions for your upgrade method.
  6. Plan for the tasks that must be performed after the ESXi host upgrade:
    • Test the system to ensure that the upgrade completed successfully.
    • Apply a host's licenses. See Applying Licenses After Upgrading to ESXi 6.5.
    • Consider setting up a syslog server for remote logging, to ensure sufficient disk storage for log files. Setting up logging on a remote host is especially important for hosts with limited local storage. vSphere Syslog Collector is included as a service in vCenter Server 6.0 and can be used to collect logs from all hosts. See Required Free Space for System Logging. For information about setting up and configuring syslog and a syslog server, setting up syslog from the host profiles interface, and installing vSphere Syslog Collector, see the vSphere Installation and Setup documentation.
  7. If the upgrade was unsuccessful and you backed up the host, you can restore the host.