Data Center Racks Getting Taller, Wider, Deeper

Dell-booth-rack

An attendee at last week's Open Compute Summit checks out a rack full of servers at the Dell booth. Dell is among those designing 23-inch hardware for the new Open Rack, which reflects a growing shift toward non-standard racks. (Photo: Colleen Miller)

The Open Compute Project initiative to develop a wider rack for data center equipment seeks to standardize a trend that has been developing for several years. Racks have been getting taller, wider and deeper for some time, according to IMS Research.

The growing adoption of non-standard racks is driven by the need to pack more servers into data center real estate, improve airflow management and fit more cabling into cabinets. Back in 2010 we noted some hyper-scale data center operators using racks as tall as nine feet, building up rather than out to pack the most server density into their square footage.

This week IMS Research reported that the height of enclosures is growing, with shipments of 48U racks forecast to grow an average of 15 percent annually over the next five years, compared to a projected average growth rate of 5 percent for the standard size.

A standard server rack is seven feet high and can accommodate 42 units (42U) of rackmount server equipment in a 19-inch wide slot. There are many options in rack size, with manufacturers offering enclosures that are up to 23 inches wide (a size often used for telecom equipment) and height options ranging from 44U and a nine-foot tall 58U rack.

Companies using extra-tall racks include Microsoft, which has developed custom rack designs featuring 57 rack units. One rack unit is about 1.75 inches in height.

Others are going wider. Last week the Open Compute Project outlined plans for Open Rack, which will seek to set a new standard for rack design for hyperscale data center environments. Open Rack provides a 21-inch wide slot for servers, expanding upon the 19-inch  standard.

Logistical Barriers to Ultra-Tall Racks

The standard 42U cabinets account for nearly two-thirds of all enclosure shipments globally, according to IMS, but this share will decline as shipments of taller racks increase. But before you go ordering nine-foot high racks, be sure to measure the entrances to your loading dock and data hall.

"The growth may be limited to 45U and 48U racks, given the logistical limitations associated with racks of 51/52U or higher," said Liz Cruz, an analyst with IMS Research. "Transporting and moving in racks of this size is made difficult by truck height restrictions and doorway openings to most data centers. 48U cabinets may prove to be the practical limit to enclosure sizes for this generation."

In terms of width, the current standard is 600mm. Going forward, IMS projects that shipments of 750-800mm wide cabinets will grow at nearly twice the rate of 600mm cabinets. In terms of depth, the 1100mm category currently accounts for the greatest share, but 1200mm will grow faster than any other depth in percentage terms.

These trends are driven by the need to manage more cabling and more heat within the enclosure as new servers pack more power into the same form factor. "Growth in power densities are not expected to level out any time in the near future, which means neither will enclosure sizes," Cruz concludes.