Zoning, part 3: Zoning schemas
Zoning is a fundamental management technique that basically controls who can see what in a storage area network (SAN). The following is part 3 of a three-part series on zoning.
Now that we understand zoning and how it works to stop servers from mounting all the LUNs it can see in a fabric, lets quickly wrap up by identifying common zoning schemas.
Common host
Common host with the SME environment is the most common zoning schema. This has a zone per operating system, server manufacturer or HBA brand, or some similar approach. This offers a fairly simple approach. After all, NT servers will play well with each other. QLogic's HBAs will play well together. So you have a zone consisting of all the common servers, plus the storage devices they need to access.
Single target multiple initiator
Traditionally, many storage subsystems had a rule that any port on an array could only be accessed by multiple servers using the same operating system. Customers who started with the common host approach, but then wanted better granularity in their zoning, saw the benefit of having each zone consisting of one port on one storage array with all the devices that were allowed to access that port. This also made it visibly easy with zoning to monitor that they were following the arrays operating system support guidelines.
Single initiator multiple target
Increasingly common in heterogeneous SANs, this approach comes from a simple premise -- SCSI initiators (servers) do not need to talk to other SCSI initiators. Therefore, a very robust approach to avoid any potential problems with servers upsetting each other is to have one server or indeed only one HBA in any zone, and then also put into that zone all the storage devices that the host is allowed to talk to.
Single initiator single target
This is the ultimate in security, as we are keeping our zones to their absolute usable minimum size and so providing maximum security from our zoning. This has been used very successful in a few cases but is not so common. Without good software it is hard work to set up and manage.
Summary
As with all things, the approach you use will depend as much on your technology as how you operate. One thing is for sure. You should think about it, choose an approach and use it fully and robustly.
Remember, zoning is not the answer to all your problems. But it is a vital part of storage provisioning. Start off on the right foot even if you think it is overkill in a small storage area network. Once you get going in the right direction, it will be easier to continue with a robust and reliable approach.
Happy zoning everyone.
About the author: Simon Gordon is a senior solution architect for McDATA based in the UK. Simon has been working as a European expert in storage networking technology for more than 5 years. He specializes in distance solutions and business continuity. Simon has been working in the IT industry for more than 20 years in a variety or technologies and business sectors including software development, systems integration, Unix and open systems, Microsoft infrastructure design as well as storage networking. He is also a contributor to and presenter for the SNIA IP-Storage Forum in Europe.
