I’ve been doing VMware Design Reviews lately and so are my colleagues of the PSO department. A Design Review is quick scan of your design documentation by a VMware consultant. The consultant will hold your docs against best practices and propose changes to the design.
One of the things we encounter on a regular base is that admins took the easy path for their Storage Design zoning. So what’s zoning? In short: a way to partition your fabric into smaller subsets. These small subsets provide you with a better security and less interference.
You can do zoning in two ways, Soft and Hard. With “soft zoning” you use the device WWN in a zone without any restrictions to what port this WWN is attached. With “hard zoning” you put the port into a specific zone. So what do I prefer? I would prefer “hard zoning” because you need to know how your devices are connected and it makes troubleshooting a lot easier.
So now I’ve chosen a way to zone I can just write down all my port numbers, create a zone and drop them in and I’m done… Well not so fast, that’s another choice one has to make before you start. How am I going to zone, single initiator zoning or multi initiator zoning? So what’s a single initiator zone: a single hba in a zone with the target device(s). And a multi initiator zone is all initiators that need to communicate with a device(s) in one zone. As one can imagine multi initiator zones are really easy to setup but definitely not my first choice.
Single initiator zones are the way to go. If there’s no need, and for ESX there isn’t, for initiators to be able to communicate with each other then they shouldn’t be able to. Not only is this more secure, because initiators can’t communicate with each other, it also cuts out a lot of rubbish on your fibre. Rubbish as for instance “Registered State Change Notifications”. Although RSCN storms don’t occur that often anymore as they used to it’s still a risk of contention and should be avoided when possible. So if you’re doing a design or preparing for one keep this in mind: Single Initiator Zones are the way to go!
There are a whole bunch of good articles on the net about zoning, read them you might learn a thing or two:
- TechTarget.com: part1, part2, part3
- Storage Networking 101: Understanding Fibre Channel Zones
- Single HBA Zoning