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Top questions to consider when consolidating SANs

Small to midsized businesses (SMBs) frequently have to deal with disparate storage area networks (SANs). For example, many companies start with an entry-level system and later must add a larger, more sophisticated one. SAN consolidation usually has two different meanings depending on the point of view. It either means reducing the number of multiple separate SAN fabrics (networks) to a more manageable number, or doing the same to multiple separate SAN storage systems.

The value of SAN consolidation comes from significantly reduced management. It is intuitive to see that it is far easier to manage a consolidated SAN than multiple SANs. Consolidated SANs also benefit from fewer software licenses, lower maintenance, reduced real estate, power, and cooling. In the unique case of the consolidated Fibre Channel (FC)

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SAN fabric, there is the benefit of a reduced number of domain names as well. The FC specification has a theoretical domain limit of 239. However, Brocade's tested limit is 50 and Cisco's tested limit is 40.

Successful SAN fabric consolidation depends upon detailed understanding of your current and future needs, careful detailed planning and disciplined execution of that plan. Critical questions to answer and plan for include:

  • How will the consolidated SAN grow to meet the future needs of the organization?
  • How does the consolidated SAN support the required throughput and/or IOPS (both now as well as future requirements) and allow prioritization while providing secure separation for different applications?
  • Where are the potential single points of failure, if any? If single points of failure are acceptable, what will be put in place on the consolidated SAN to mitigate failures? (Such as dual systems, dual fabrics, multipathing, load balancing, etc.) If one application goes down, how will the others be impacted, if at all?
  • Does the consolidated FC SAN fabric require a director class or can dual high-density switch (64 to 128 ports) accomplish the same thing for much less cost?
  • Does the consolidated iSCSI SAN fabric require data center class Ethernet switches or can dual standard high capacity Ethernet switches accomplish the same at a significantly reduced TCO?
  • How will the migration from multiple SANs to a consolidated SAN be accomplished with minimal application and user disruption?
  • How will multiple separate applications be managed? Multiple administrators may have responsibilities to manage on the same physical fabric. How do you ensure secure separation among administrator responsibilities?
  • Will the TCO of the consolidated SAN (that is, operating expenses [OpEx] and capital expenditures [CapEx]) be less than the multiple SANs? If not, how is it still justifiable?
  • Assuming the answers to those questions are all positive or mostly positive, what do you do next? The answer is preparation.

  • Pick your vendor(s) -- partner(s).
  • Plan the implementation.
  • Communicate in detail with all of the departments, administrators and application owners about the transition. Over communicate if necessary.
  • Document everything.
  • Follow up to learn from mistakes made and to improve for next time, And yes there will probably be further consolidation meaning a next time.
  • About this author: Marc Staimer is President and CDS of Dragon Slayer Consulting in Beaverton, OR. He's widely known as one of the leading storage market analysts in the network storage and storage management industries.

    This was first published in September 2008

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