One of the great features of VMware vSphere is the capability to boot VMware ESXi from USB flash — eliminating local storage and array controllers can reduce the acquisition and operational costs for hypervisor hosts.
Now with VMware ESXi 5, it is possible to perform an automated installation to USB storage. Simply specify usb-storage as part of the install command in an automated install script. For example:
install --firstdisk=usb-storage --overwritevmfs
For more flexibility in a single script, multiple disk types can be specified; they will be tried in order. Below is an example install command from a script for HP servers. If USB flash is not installed, the on-board SAS disks will be used. If neither are present — such as when installing virtual ESXi systems — generic local storage is the last resort.
install --firstdisk=usb-storage,hpsa,local --overwritevmfs