What you will learn from this tip: How to develop an effective zoning plan and implement it with a minimum of hassle. Need a downloadable copy? Go here.
Dividing your SAN
Zone your SAN in five steps
1. Decide on a zoning scheme.
The most important part of zoning a SAN is deciding how many zones you need and which servers, storage and users need to be in each zone.
There are a number of critical questions that need to be answered when choosing a zoning scheme. For example, how much granularity do you need in your zones and in turn, how many zones do you need? Do you want to have a single server in each zone to minimize interactions, or do you want to allow multiple servers to access the same storage device? How often are you likely to want to change the zone assignments of various devices? Do you want to put your tape backup system in a separate zone?
Not all the considerations relate directly to the abstract architecture of your zoning system. For example, it is usually best to group similar elements in each zone. In other words, put different operating systems in different zones and try to use the same brand of hardware, such as HBAs, in the same zones. This can cut down on interoperability problems.
2. Analyze all components.
One critically important part of designing a zoning scheme is analysis. In other words, making sure that all the servers, devices, etc. are members of the right zones –- or at least a zone. Zones with only a single member and devices or WWNs (World Wide Names) that are part of a configuration but not part of the fabric are among the things to look for. Many hardware and storage management software vendors provide utilities to help you locate these kinds of problems.
3. Pick a zoning method.
Zoning is commonly divided into hard zoning, which is enforced by the hardware, and soft zoning, which is enforced by the name server. Hard zoning, which ties devices to specific ports on the SAN, is more secure but more difficult to modify, and hence more difficult to manage. Soft zoning, which typically uses devices' WWNs to assign devices to zones, is more flexible and easier to change, but it is less secure. Note that, in most SANs, it is possible to mix port-defined and WWN-defined items in the same zone, although the result is usually a soft zone. There are also hybrid zoning methods, such as Brocade's approach that combine hard and soft zoning.
The question of zoning method should be considered after the zoning plan is worked out, because the kind of zones you need will have a major impact on your choice of method. For example, if you need a high level of security and you're unlikely to be moving devices, you will probably want to use hard zoning only. If flexibility is your goal, you will be better off using soft zoning.
4. Configure your zones.
Configuring the zones on your SAN is the fastest part of the operation when everything goes right and the longest, most frustrating part when it doesn't. This is where mistakes in the preceding steps, especially analysis, will show up.
5. Test everything.
Once your zones have been configured, test the configuration thoroughly. Make sure the appropriate storage is visible to the appropriate servers and users. Be sure to test your backup and restore systems against the zones.
For more information:
Crash Course: Zoning
Topics: SAN routing and partitioning
Tip: How to troubleshoot SANs using WWN zoning
About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years, he has been a freelance writer specializing in storage and other computer issues.
This was first published in May 2005