Rodos just reported on twitter that it looks like Boot From SAN is supported for ESXi. Unfortunately the KB article Rodos refers to in his tweet, kb.vmware.com/kb/1015000, is incorrect and Boot From SAN is not supported for ESXi. I’ve already reported this internally and hopefully the KB article will be fixed soon. The correct statement can be found in the install guide and is as follows:
Installing on a Fibre Channel SAN is supported experimentally. Do not attempt to install ESXi with a SAN attached, unless you want to try this experimental feature.
Source: ESXi Installable and vCenter Server Setup Guide (page 20)
For those interested in what “experimental” actually means, read this section on the VMware website.