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Cisco SANs: Where do you begin?

February 20, 2012 at 1:07 pm PST

I spent two weeks over at the Ask the Expert forums, and I came to the realization that often our customers are bombarded with facts, figures, speeds, feeds, features, buzzwords, comparisons and functionalities for which they’re not sure which ones they must have while others they can live without or are a convenience.  So I figured I’d toss out what I think are the top features for building an MDS Storage Area Network.   Some may be obvious and others you might shake your head or light up the torches.  They’re not in any particular order as your mileage varies from mine.  I’ll probably skip those that are obvious like “hot swap power supplies” and other oh so exciting abilities…

The first set I usually refer to as the holy trinity of features as they constitute the foundation of the connectivity… VSANs, Port-Channels and TE Ports.  They’ve been around literally forever on the platform and for good reason, they’ve been part of the hardware’s DNA since it’s inception.  Additionally, if you walk down the hall to the folks that manage your LAN, you’ll find out that they’re using pretty much the same concepts and features as you (VLANs, Port/Ether-Channels and Trunking or 802.1q).  So, if those guys are managing hundreds or thousands of switches and routers, there’s probably something worthwhile here.   It’s also a pretty good chance that they are using them for the very same reasons that you are:

  • VSANs: Isolation of fault domains.
  • Port-Channels: High Availability and load-balancing of InterSwitch Links (ISL)
  • TE_Ports: The ability to run multiple VSANs over the same ISL leveraging frames tagged with the VSAN ID and enforced in hardware.

Next on my list is NPV Mode aka N_Port Virtualization.  I grew up in the era of 16 port SAN switches and like rabbits, they multiplied, and so did their domains, and don’t get me started on the upgrades…  You had top of rack designs that involved dozens of small switches and this tsunami of small switches was slowed down by the emergence of the high density directors with hundreds of ports, first 128 then 256 now over 500.  Lots of small switches met their demise..

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