Diskless Boot

While commenting to a tweet of @alecmuffet a question arised in my head: Why do many people talk about SAN boot and why do people seldomly ask for NFS boot? Asides from my opinion that systems should be able to boot without help from the outside (debugging is much easier, when you have an OS on your metal), SAN boot looks to me like combining the worst of all worlds. You depend on centralized infrastructure, you have to put HBAs (at least two) in every server, you have to provide an additional fabric, encryption is still an unsolved problem. On the other side you have NFS, deduplication and cloning is a non-problem when you configure your boot environment in a clever way, encryption is available by the means of IPsec. Caching to get load from the network is possible by CacheFS for example. Or think about the combination of NFS boot with the snapshot/clone function of ZFS to clone you boot environments? So why is everybody looking in the direction of SAN boot instead of using NFS boot, when they look at centralized boot storage? The issue of needing an additional fabric is known, so solutions are developed, but instead of simple going in the direction of NFS the industry is running into the direction of blocks over IP or blocks over Ethernet. Strange world …