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Strategic decisions for managing SANs

Storage is now so important it is essential to make strategic decisions, and then make them work. This applies to all levels: Product selection, SAN design, implementation and management.

Early in my IT career, when I was a programmer, I was told that choosing a software design methodology, then using it properly, was more important than which methodology you actually chose. Having worked in many areas of IT, and most recently storage and SANs, I think you can apply a version of this rule to almost any case.

In an increasingly complex environment, it is vital that you decide on your strategy, standardize wherever possible, document clearly and accept the fact that some things do not fit the standard, in which case you make sure the exception is clearly justified and documented.

For example, do you have a SAN consisting of a single fabric or dual-redundant fabrics? Do you dual-attach everything or only those devices that need the higher levels of high availability (HA)? This decision is becoming a non-argument. The cost of HBAs and the per-port costs of switches have decreased steadily, and the incremental cost of doing things properly is small compared to the cost savings of standardization. Therefore, I would recommend in almost every single case that you use two fabrics and that the two fabrics should be configured identically. Every server should have two HBAs, one connected to each fabric, etc. This gives you consistency so that your documentation is

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simpler, your management procedures are simpler and TCO is reduced.

There are exceptions today. In general, dual-connection, direct-Fibre Channel-attach tape drives offers limited benefit -- at least until the backup software world catches up. And of course, if you are connecting tape libraries through Fibre to a SCSI router, then this will also tend to lead to single connect.

Also, if you have servers that only have space for a single HBA, you could keep things more standard by using a dual-port HBA.

Most importantly, making this a strategic decision forces you to think through the implications more clearly so you end up making better, more flexible and more "future-proof" decisions.


About the author:

About the author: Simon Gordon is a senior solution architect for McDATA based in the UK. Simon has been working as a European expert in storage networking technology for more than 5 years. He specializes in distance solutions and business continuity. Simon has been working in the IT industry for more than 20 years in a variety or technologies and business sectors including software development, systems integration, Unix and open systems, Microsoft infrastructure design as well as storage networking. He is also a contributor to and presenter for the SNIA IP-Storage Forum in Europe.

This was first published in November 2002

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