Specifications

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Summary of Best Practices for Storage Area Networks

2 Zoning

Zoning is the way Storage Area Networks (SANs) keep devices isolated from each

other; this has implications for security, fabric stability, and resource management.

Without zoning, it would be very common for a problem on one host to be able to affect

every host in the fabric; without zoning the problems this can cause are difficult or

impossible to troubleshoot.

A number of zoning implementation methods are listed below, starting with the worse

case and progressively improving the granularity of zones.

 One-big-zone, also known as no zoning (worse case)

 Zone by operating system

 Zone by HBA vendor

 Zone by application

 Zone by cluster groups

 Zone by initiator port (best scenario)

The worst case scenario of one big zone (effectively, no zoning) means that all devices

can communicate with all other devices. This approach may be workable and stable for

very small (1-5 hosts and a single storage system) SAN environments, but it is strongly

advised to never use this method.

Creating zones based on operating systems, HBA vendor and or by application

improves the granularity, or scope, of individual zones. This reduction in scope is due

to the operational functionality of various components. Some operating systems will try

to access the resources of any device that it can, or has ever been able to, access.

When HBA adapters register with the nameserver, they normally specify whether they

are an initiator or a target. However, some ports will register as both (target and

initiator) and thus cause potential confusion when a host system requests information

about what target devices within the SAN environment are accessible.

The suggested implementation method is to create zones for individual initiator ports

(typically a single host port) with one or more target ports. Although fibre channel

standards and switch vendors allow zones to be created using device WWNN (world-

wide node names), this practice should be avoided. When a WWNN is used in place of