Brocade fibre zoning; what is the benefit?

[aperia]

We are adding a 3Par 7200 SAN to our existing fibre fabric which already has a P2000 G3 in production, all attached via 2 Brocade 8Gb fibre switches. We currently have no zoning at all and have had no issues since implementing the SAN for a couple years. I have just learned about zoning from our HP tech who guided me through initializing the SAN and using the 3Par management console.

My question is why is zoning useful? We have been using our current SAN with no zoning for years. I can see a benefit in 1 or 2 scenarios, but to me zoning is a useless, overly complex mechanism which does... what?

In our environment all our initiators will need connectivity to both SAN devices. We will be creating new and moving around existing volumes on both SANS to all hosts. Implementing zoning would make the SAN a nightmare to manage. Why would I limit a host to access only one part of the SAN? Security is a non-issue on our fabric. I don't see an instance where one could hack the fabric. None of our hosts can see any other host on the fabric. Even if they do, is there an issue with that? We might have a scenario where we remove the HBAs from one server and plug them into another. Why would I want to worry about aliases and ports in that case? Mapping/exporting LUNs to hosts is controlled on the SANs. I don't create volumes which are available to all hosts initially, but if need be I want to quickly be able to assign a LUN to one machine and unmap it from another or make it available to a cluster.

Aside from creating more work, what is the benifit of zoning if I am not concerned with security (should I be???) and don't care that Luns or ports are locked down from host to target? A guide from Brocade states it is important because, "isolate servers from each other.". I don't understand how one host could see a volume that is explicitly mapped to another server and on top of that is denied access to all others via the SAN.