As companies seek to cram more computing power into precious data center space, part of the question is how to organize servers and other necessary IT infrastructure. And the backbone of that organization scheme is the cabinet (or rack), which is designed to bring order to a potentially chaotic mass of servers, power distribution units, cables, switches and other gear. Here’s a look at a few of the major trends in data center cabinets.
What’s Driving Data Center Cabinet Trends
Several critical concerns in the data center underlie the trends in cabinets and racks. Foremost is the ever growing demand for IT resources: companies must keep pace with customer demands on their infrastructure, whether the customers are outside or inside the company. But apart from costly expansions to existing data center facilities or more-costly construction of new facilities, these companies have few options beyond increasing power density. Virtualization can help by ensuring that usage of existing resources is maximized, but eventually the supply is tapped out.
But cramming more servers into a given space—culminating with microserver and blade server architectures—has its own associated difficulties, not the least of which are cooling and power distribution. Cooling is a particularly acute problem, as eventually, power densities in a cabinet reach the point where air cooling is insufficient. Liquid cooling options are available, and they offer more-effective cooling, but they come with their own set of difficulties and higher infrastructure costs (relative to similar air-cooling systems).
Cabinet Size: Going Up and Going Out
Perhaps the most natural first response to the need for more cabinet space in a data center is to use bigger cabinets—and that’s what the industry is moving toward. A recent IMS Research press release (“IT Enclosure Dimensions Grow—Upwards and Outwards”) notes that “increasing server depths, more cabling within cabinets, the need for airflow management, and the desire to maximize floor space within data centers are driving larger racks and enclosures.” IMS Research forecasts 15% annual growth of 48U racks over the next five years—these racks offer nearly 15% more vertical space compared with the standard 42U rack.
Naturally, the move to taller cabinets owes to companies looking for more room after maximizing (or nearly so) their horizontal space; vertical expansion is often the final frontier. At some point, however, even vertical growth is limited—and not just by the height of the ceiling in the data center. IMS Research analyst Liz Cruz observes, “The growth may be limited to 45U and 48U racks, given the logistical limitations associated with racks of 51/52U or higher. Transporting and moving in racks of this size is made difficult by truck height restrictions and doorway openings to most data centers.”
In addition to size, weight is also a concern. Mike Kendall, Group Manager of Options and Infrastructure, Industry Standard Servers and Software for Hewlett-Packard, notes that “it’s not only about how much weight [the rack or cabinet] can hold when loading the racks in the data center (the static load capacity), it’s also important to consider the dynamic loading weight, or how much weight it can accommodate when being shipped fully loaded.” Imagine a tower built with toothpicks—it might be able to stand on solid ground, but give it a little shake and it could fall apart. Thus, depending on whether the cabinet is delivered full or empty, maximum size may be limited by both practical and financial factors (designing a cabinet to handle shipping stresses while fully loaded will necessarily incur a cost premium over less sturdy cabinets).
Part of the increase in cabinet size, however, is not simply to make room for more servers. As more equipment is crammed into a given space, less air is available to enable cooling and making way for cabling to all the equipment can quickly become problematic. According to IMS Research, “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.” But this isn’t necessarily surprising: last year (“A Data Center Rack by Any Other Name Is Still a Rack?”), Kendall noted that “we’re also starting to see an increase in use of 1,200mm depth racks, particularly in HPC systems which require extra clearance for cooling. 1,200mm deep racks are also becoming more popular to accommodate for tile spacing and extra room in the back for cable management.”
Cooling the Cabinet
Improving airflow by adding more space to a cabinet is beneficial for cooling purposes, but it is only effective up to a point. Beyond certain power densities, air simply becomes impractical as a means of effectively cooling the equipment; high-performance computing (HPC) is one area in which this is particularly problematic. Thus, liquid cooling is a far from novel means of keeping equipment in high-density deployments from overheating. The means of keeping the equipment cool ranges from the use of chilled water to carry heat from the cabinet to the more-extreme immersion cooling, where servers are submerged in vats of coolant.
DatacenterDynamics (“Submerged IT – do you dare?”) identifies air cooling as the “low-hanging fruit,” meaning it is an easy and relatively convenient means of cooling compared with systems that use liquid (whether immersion based or otherwise). For most data centers, air cooling is the most economical approach, so liquid-cooled or immersion-based cabinets probably won’t flood the market (pun intended), but these types of cabinets do have very real and very important applications in HPC and other high-density deployments. And as these high-density deployments increase, so will use of cabinets that employ some form of liquid cooling.
For the rest of the market, however, movement will be toward larger cabinets that also provide more cable-management capabilities to improve airflow and thus cooling efficiency.
Cabinets in the data center are growing mainly in response to the need for more IT resources in limited space. This increase in resources can manifest itself as higher power densities, larger (deeper) server units, more cabling and so on. The result is the need for more space, more cooling capability or both. Companies are thus increasingly targeting cabinets that provide more space (both vertically to add more servers and other equipment and horizontally to enable better airflow, leave more room for cabling and accommodate larger servers) and, in some instances, more cooling capabilities. For high power densities, liquid cooling becomes almost a necessity; some companies are even employing cabinets (which might better be called “vats”) for actual immersion of equipment in a coolant liquid.
For most companies, however, the trend of greatest import is larger cabinets—taller, wider and deeper. The market is moving in this direction, but growth in cabinet size is limited by practical considerations: particularly, the size of doorways into data centers, ceiling heights, truck heights and similar dimensions that hamper the ability to move or install these cabinets.
Photo courtesy of nationalrural