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It's getting harder to distinguish between a low-end enterprise array and a high-end midrange array--but there are still some important differences.


High-end midrange arrays and low-end enterprise arrays look awfully similar these days. During the last few years, features like clustering, mirrored cache, replication and snapshots have trickled down from enterprise arrays, while low-priced SATA drives have moved up to enterprise arrays to further confuse the already somewhat arbitrary array classifications.

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How we define high-end midrange arrays
Identifying which high-end midrange arrays to include in this article wasn't easy. Depending on how they're defined, there are from 40 to almost 100 different midrange array models. This article focused on models that users would most likely consider an upgrade to their current midrange model or as a replacement for an enterprise-class storage array.

We used the following four general characteristics as the criteria to define high-end midrange arrays:
  • The midrange array must contain two controllers in an active-active or dual-active configuration


  • It must support some form of replication software (asynchronous, synchronous or snapshot)


  • It must offer support and services either natively or through a value-added reseller


  • The arrays are rack-mountable
If a vendor had multiple products that met all of these conditions (which many vendors had), this article attempted to limit its coverage to only the highest end model of the product line.

The midrange array category is getting bigger, a catchall of low-end commodity systems and high-end arrays with specialized features (see "How we define high-end midrange arrays," at right). But there are distinct differences in array architectures in the midrange category that vendors don't advertise. These include:

  • Low-end midrange arrays are typified by high-capacity SATA drives often with minimal or no storage management features in the storage array controllers such as replication or high availability. Low-end arrays may come with only one controller or two controllers configured as active-standby.


  • High-end midrange arrays contain active-active or dual-active controllers, and generally support a mix of disk drive options such as Fibre Channel (FC), SAS, Fibre Attached Technology Adapted (FATA) or SATA. Some also offer advanced storage management features like asynchronous replication, snapshots, thin provisioning and automated tiered storage that ship as standard or optional features.


  • Low-end enterprise arrays closely resemble high-end midrange arrays but have controllers in active-active configurations; may use proprietary ASICs for faster processing; and deliver higher levels of availability, reliability and performance for applications that have little tolerance for service disruptions.
Prices for similarly configured high-end midrange and low-end enterprise arrays are often comparable, but there are significant differences between the two classes in feature functionality and software licensing fees. Terms like "dual-active controllers" and "array-based replication" contain nuances in meaning that uninformed buyers can misinterpret, which can impact the midrange array's cost and management capabilities. Free or low-cost replication software, heightened integration between array snapshot and third-party backup software, and the support level a vendor can offer are the top areas potential users must evaluate.

This was first published in May 2007

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