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The best way to expand a SAN

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Adding SAN intelligence
SANs have transformed storage from a system-bound resource to an easily scalable shared network resource. The next evolution of SANs will likely include a higher level of virtualization that reduces the vendor dependency seen in contemporary SANs, and an increase in intelligence to simplify and automate many of the complex manual tasks performed by storage administrators today.

However, there's considerable controversy about where to embed this added

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intelligence in the SAN. There are several solutions:
  • Array-based virtualization puts the intelligence in the storage array; Hitachi Data Systems' TagmaStore is the prime player for this method.


  • Switch vendors Cisco Systems Inc., Brocade Communications Systems Inc. and McData Corp., as well as EMC Corp. with its split-path architecture Invista product, put the intelligence in the switch or router.


  • IBM Corp.'s SAN Volume Controller (SVC) uses an inline appliance approach to provide virtualization.

Computing platforms
When growing a SAN in both capacity and performance to meet application requirements, the computing platform can play a crucial role, especially for large and very large SANs. Determining the right computing model to enable an application to meet its performance, availability and scalability objectives is as important as choosing the right SAN architecture.

Contemporary application trends such as Web services, service-oriented architecture (SOA) and software as a service (SaaS) require a platform that scales linearly, easily and as close to infinitely as possible by simply adding computing resources, including storage. Grid computing is touted to be this platform. Grid computing or grid clusters are akin to a utility in which semitrusted nodes perform assigned tasks. Key functions performed by grid computing include scheduling of nodes and resources, data virtualization that makes information available whenever and wherever it's needed, provisioning of available computing resources and resource management.

At its core, grid computing is based on an open set of standards and protocols such as the Open Grid Services Architecture (OGSA) that enables communication across heterogeneous, geographically dispersed environments. Virtualization of computing resources is at the core of grid computing, but unlike traditional virtualization technologies that virtualize a single system, grid computing virtualizes vast and disparate IT resources.

The biggest stumbling block when growing today's SANs is the lack of multivendor product interoperability. Consequently, using products from as few vendors as possible is advantageous. Storage applications from mirroring, snapshots and replication, to virtualization and transparent data movement rarely work outside very specific single-vendor product configurations (see "Adding SAN intelligence," at right).

This was first published in July 2006

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