Zoning 101: Why zone?

What you will learn from this tip: Zoning can offer a number of benefits for your SAN. Read about the advantages of zoning, as well as an explanation of the different methods.

Zoning is one of the most common tools for managing and securing a SAN. It provides an easy method to limit which groups of users can connect with which storage volumes, as well as matching operating systems (OS) with their storage.

Depending on how it is done, zoning can offer a number of benefits:

• Security. Zoning keeps users from accessing information they don't need.
• Manageability. By splitting the SAN up into chunks, zoning makes it easer to keep track of devices, storage and users.
• Separation by purpose. Setting up zones to reflect operational categories, such as engineering or human resources, organizes storage logically. It also makes it easy to establish specialized networks for testing or other purposes.
• Separation by operating system. Putting different OSs in different zones reduces the possibility of data corruption.
• Allowing temporary access. Administrators can remove the zone restrictions temporarily to allow tasks such as nightly backup.

The two most common methods of zoning are name server, or "soft" zoning, and port, or "hard" zoning. Name server zoning partitions zones based on the World Wide Name (WWN) of devices on the SAN. It is the easiest to set up and the most flexible, but it is the least secure.

Port zoning allows devices attached to particular ports on the switch to communicate only with devices attached to other ports in the same zone. The SAN switch keeps a table indicating which ports are allowed to communicate with each other.

The easy way to think of the difference is to picture soft zoning as a telephone directory and hard zoning as call blocking. Soft zoning won't tell you the port number for any device outside your zone, but it won't prevent you from sending packets to any port on the SAN. Hard zoning won't let you communicate with any port not on the "approved" list.

Hard zoning is more secure, but it creates a number of problems because it limits the flow of data to connections between specific ports on the fabric.

The type of zoning that will work best on your SAN depends on the characteristics of the SAN. For example, if you expect to be switching cables frequently for load balancing or troubleshooting, soft zoning is more convenient because such switching won't disrupt the SAN. If security is paramount, you probably want hard 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 20 years, he has been a freelance writer specializing in storage and other computer issues.