Very good question and one that comes up a lot when folks are trying to figure out their SAN strategy from both a manageability and cost perspective.
There was a recent survey done by the CIO council in Washington, DC that touched on this subject. The outcome of the survey showed that there were three different buying methods used by the major corporations implementing SANs.
The first approach was to use "competing islands" managed by a single enterprise storage group created within the corporation. This method avoided vendor "lock-in" and kept costs competitive by having the two primary storage vendors compete for each new initiative.
The second method used "competing SSPs", where the company outsourced its storage requirements to the SSP community and let the SSPs choose the storage vendor. The SSP would then provide the customer with either on-site or off-site managed storage on a cost per gigabyte basis, with an associated up-time SLA.
The third method was to use a B2B method of purchasing "spot market storage" by trading B2B services with excess capacity owned by the SSP marketplace. This allowed buying "flexibility while allowing the customer to avoid long-term SSP contract lock-in."
Of course, these approaches were used by major corporations doing millions of dollars worth of storage purchases each year. For a smaller shop implementing a SAN for a single data center, a single vendor sometimes makes sense to get that "one throat to choke" feeling. It also makes the implementation and management easier since everything is pre-certified by the single vendor. I usually see a "tiered" model at most sites where there may be a cheaper modular solution for non-critical applications like file/print and another higher-end solution for mission-critical database type applications. This will allow your storage group to "charge-back" storage requirements to business functions based on a performance and availability SLA.
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This was first published in April 2002