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Troubleshooting production fabric environments

Tips for troubleshooting in a SAN environment

Troubleshooting production fabric environments
By Matthew Sharib

Many companies implement a SAN environment without knowing what is required for troubleshooting and problem determination. In some cases a problem on a fabric could indeed cause a central failure of a SAN no matter how much redundancy is built in. I have learned that it is a necessity to have a completely separate fabric that can be used for testing. You can replicate a problem to the separate fabric and then troubleshoot the problem.

Why? There are many problems that can happen in a portion of a fabric that can affect the entire fabric. For example, switch configurations can work correctly for months and suddenly, when a driver is updated or a new HBA is introduced, the whole fabric starts reinitializing randomly. That's just one problem that can occur in a fabric.

There are two methods that I have seen for setting up a separate fabric.

Separate zones:
As storage vendors release storage frames with built-in security to assign LUNs at the WWN level, more and more companies are abandoning zoning as it is most popularly used to disable NT and Unix machines from being able to see each other's disks. Having separate zones for a production and test area is a good idea. If these zones are introduced, they should be hardware enforced at the port and not through WWNs. Hardware zoning is the only way to completely segment an N-Port device from a different zone.

Separate switch:
In some cases it would be more efficient to have a completely separate switch connected to a storage frame. The main reason for this is that fiber ports on some of the newer storage frames use different emulation modes to be compatible with different HBAs available on the market. If your company decides to test HBAs that require a different port-emulation mode on your frame, you may need to have a separate switch connected to it. If a testing zone is planned carefully however, you can zone in a port on a storage frame to allow you to do this without the additional storage.

My experience is with Brocade switch fabrics and may not be applicable for different switch vendors. If you're using a different switch vendor that does not support hardware zoning, explore other options for testing environments.

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Related Book

Fibre Channel for SANs
Author : Alan Frederic Benner
Publisher : McGraw-Hill
Published : Mar 2001
Summary :
PRACTICAL ROADMAP FOR DESIGNING AND DEPLOYING A SANFibre Channel has come into its own as the defining network architecture for Storage Area Networks (SANs), which are proving critical for managing the volume and complexity of data generated by Internet-era applications.

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