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Implement zoning in storage

Which zoning for you? This tip discusses pros and cons.


Implement zoning in storage
Rick Cook

While zoning a SAN provides a number of advantages in storage administration and security, there are several ways to do it with different benefits and drawbacks. In addition to zoning at the device level or LUN level, there is also hard, soft and persistent zoning.

As the name implies, soft zoning is the most permissive. This is also called name server zoning because it is done using a name server databases in the SAN director. Since the database can contain both port numbers and WWN numbers and translates between them, administrators can shift devices among ports without changing the zoning configuration. One problem with soft zoning is that some HBAs (Host Bus Adapters) won't cooperate with soft zoning.

Hard zoning uses a routing table, also located in the director, which assigns devices to zones only by WWN. This is more limited since it doesn't take the port number into consideration, which makes it harder to shift devices between ports.

Persistent binding is implemented in the HBAs rather than the director. Configuring a logical route across the network fabric in each adapter does it. This ties the HBA to a particular LUN. While the administrator can more easily specify storage resources in a multi-host fabric, persistent binding decreases address space and increases network complexity.

A discussion of the various approaches can be found in at white paper at:

Rick Cook has been writing about mass storage since the days when the term meant an 80K 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.

Additional Resources:
1. What's the difference between hard and soft zoning?
This white paper, titled "An introduction to zoning," does a thorough job of explaining just what its name implies. You'll learn what's different about the various types of zoning (such as, soft zoning, hard zoning, or persistent binding), and other zoning details. There's a slight McDATA slant in here, but the information is an excellent backgrounder for those new to the SAN world.

2. What are the security issues with respect to SAN environments?
In his response to this user-submitted question, SAN expert Christopher Poelker explains the different types of SAN zoning. He also delves briefly into different methods of LUN masing and how they affect security.

3. What are some SAN switch design considerations?
When designing your SAN, think about what you want to achieve. Do you really need any-to-any connectivity, or is your goal just storage consolidation? This user-submitted tip offers advice on when and how to use inter switch links (ISLs) for distributing zoning information.

4. How are SCSI target/LUNs mapped to Fibre Channel LUNs?
This reader wants to ensure persistent binding across boots on Fibre Channel switched networks. Our storage networking expert Marc Farley comes to the rescue.

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