Rack enclosures evolve: compacting server technology prompts cooling, cabling adjustments. (Special focus: Cabling, Wiring and Enclosures).

The major trend affecting industry-standard rack enclosures is technology compaction. Today's IT equipment is designed to be rack-optimized for efficient mounting, maximizing the utilization of valuable floor space. Equipment width and height is tightly controlled by standard EIA-310, although equipment depth is undefined.

Progressive racks typically provide vertical mounting rails, which conform to EIA-310 and are easily adjustable. Servers, telecom switch gear, keyboard/ video/mouse switches, power distribution units, hubs, routers, patch panels, uninterruptible power supplies and other IT equipment can now be mounted neatly in a rack enclosure. The flexibility of these adjustable mounting rails allow the different depths of this equipment from different manufacturers to be rackmounted.

EIA-310 mounting rails should provide square holes--as opposed to round-tapped holes--which give the increased flexibility for installing different-size cage nuts to mate with the different captive screws, commonly installed on the front bezels of rack-optimized equipment. These flexible features associated with vertical-mounting rails define a vendor-neutral, rackmount environment.

Thin servers are shipping in a 1U height form factor. With the introduction of blade servers, customers can configure a typical 42U-high server rack with up to 280 server blades. As a result, rack enclosure solutions now must provide enhanced thermal management, efficient power distribution and integrated cable management.

In most data centers, average heat loads are 1,500 watts to 3,000 watts per rack. Some applications approach 5,000 watts per rack, with up to 10,000 watts per rack predicted. Rack enclosure front and rear doors should provide maximum ventilation to promote the front-to-back airflow design prevalent in most server and storage devices, and will typically provide adequate cooling up to 3,000 watts per rack.

Usually required in the rack to provide supplemental airflow are fans, which cool between 3,000 watts and 6,000 watts per rack. Traditional roof-mounted fan trays are not effective for most server applications with front-to-back airflow direction. To cool 10,000 watts per rack and beyond, supplemental cooling is achieved with rack air conditioning. Rack enclosures should integrate the minimum ventilation features and offer a scalable suite of thermal management products to address cur rent needs and future challenges.

With a greater number of servers in a single rack, there is an increased number with dual and triple power cords for redundancy to improve their level of availability. As a result, power distribution schemes in racks need to offer higher outlet densities, while making efficient use of internal space. Power outlet strips should be mounted in easily accessible locations within the rack to preserve service clearance for rackmounted equipment.

Redundant applications might require 84 power outlets in a single 42U-high rack enclosure. For high levels of power-outlet density, three-phase input power feeds should be run to each rack, minimizing the number of individual power outlet strips required.

With the number of rackmounted devices per rack increasing and redundant power cords more common today, the challenge is to offer adequate space for cable entry-and-exit conduits, while providing organized cable containment features for protection. Sharp edges around all cable openings in the rack should be protected by grommets to avoid cutting data and power cables.

Rack enclosures help companies maximize flexibility by offering a progressive, nonproprietary feature set and an extensive line of scalable accessory products to address current and future technology trends. Maintaining a vendor-neutral rackmount environment is imperative.

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Eacueo is a product communications manager for APC, West Kingston, RI.