NAS system buying decisions


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NAS features in depth

Regardless of your company size or file-storage needs, it’s essential to consider the key NAS attributes and features to ensure you’ll arrive at a buying decision you won’t regret later. These are the key areas to look at when evaluating NAS systems:

  • Dual controller vs. scale-out NAS architecture
  • Storage efficiency
  • Unified storage
  • Virtualization

Dual controller vs. scale-out NAS architecture

Fully redundant dual-controller NAS systems have dominated the enterprise space since they first appeared on the market in the early 1990s. They scale vertically by adding disk spindles, and all components are tightly coupled and share a common pool of resources. Once the performance limit is reached, the only scaling option is to add additional NAS systems that operate independently of each other. Because they scale by adding spindles, they perform well with workloads that primarily consist of random access of small files, which represents the prevailing workload in enterprise data centers.

Conversely, scale-out NAS consists of loosely coupled processing nodes, starting with as few as two, that operate in parallel and scale horizontally by adding additional nodes. Even though the degree of parallelism among scale-out systems varies, in general, processing nodes work in concert to

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deliver files. Each time a node is added, performance of the overall system increases proportionally. For the most part, a scale-out NAS approach eliminates the need for expensive forklift upgrades to replace existing systems; instead, it makes it possible for the existing single NAS system to expand to multiple petabytes. The benefits of scale-out NAS are pretty compelling: improved performance of both I/O and throughput, improved scalability, cost reduction, simplified management by only having to manage a single large system and elevated high availability. “We predict that by 2015, 80% of all storage systems [NAS and block based] will be based on scale-out designs,” said Terri McClure, a senior analyst at ESG.

The ability to support scale-out deployments is increasingly becoming a requirement for enterprise NAS systems, and traditional scale-up systems will be gradually relegated to the SMB space. But even in the SMB space they’ll face the scale-out threat, especially from NetApp with its scale-out deployment support in Data Ontap 8. Perhaps the strongest indicator we’ve reached a scale-out inflection point is that the leading NAS vendors have all signed up to the scale-out paradigm: Dell through its acquisition of Exanet and having released initial gateway products based on Exanet (the NX3500, a NAS gateway for the PowerVault iSCSI arrays; and the NX7500, a NAS gateway for the EqualLogic array family); EMC by acquiring Isilon; HP with StorageWorks X9000; IBM with SONAS; and NetApp.

This was first published in November 2011

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