SAN/iSCSI/NAS, or any other centralized network storage, work great for shared data or HA configuration. Although technically they can be used to boot, it's not recommended, unless you need diskless nodes.
Moreover, booting from SAN volumes is complicated, as most OSes are not designed for this kind of configuration. A huge scripting effort and booting procedure is required.
SAN vendor must support platform booting a Linux server. You need to configure HBA and SAN according to vendor specification. You must totally depend upon SAN vendor for drivers and firmware (HBA Bios) to get thing work properly. General principle - don’t put all your eggs in one basket err one vendor
Proper fiber channel topology must be used. Make sure Multipathing and redundant SAN links are used. The boot disk LUN is dedicated to a single host. etc