I have been doing a bit of work with ESXi recently and came up with this little PowerShell script to quickly back up the configurations of all the ESXi hosts managed by a particular vCenter Server.
It should be run after any ESXi hosts are upgraded or have their configuration changed. A Manifest file is produced that lists the Version and Build of each host that is backed up which is useful for doing restores as these have to match if you are restoring the configuration of an ESXi host. Previous backups and their corresponding Manifest file are zipped up and copied to the Archive path.
To run this script you will need to install VMWare PowerCLI, create the Backup and Archive directories and alter the variables at the top of the script to suit your environment. It will prompt you for authentication to login to the vCenter Server so in this form it cannot be run as a scheduled task.